Adding a scale bar and north arrow to a ggplot

Hi people,

I posted a similar question to the ggplot2 mailing list and with their help 
and a lot of tinkering I got a well working function to add a scalebar to a 
ggplot plot. I could add the function to automap, but is there another 
package which would be more appropraite, e.g. sp (Roger?)?

cheers,
Paul

ps: new version of code here:

makeNiceNumber = function(num, num.pretty = 1) {
 # Rounding provided by code from Maarten Plieger
 return((round(num/10^(round(log10(num))-1))*(10^(round(log10(num))-1))))
}

createBoxPolygon = function(llcorner, width, height) {
 relativeCoords = data.frame(c(0, 0, width, width, 0), c(0, height, height, 
0, 0))
 names(relativeCoords) = names(llcorner)
 return(t(apply(relativeCoords, 1, function(x) llcorner + x)))
}

addScaleBar = function(ggplot_obj, spatial_obj, attribute, addParams = 
list()) {
 addParamsDefaults = list(noBins = 5, xname = "x", yname = "y", unit = "m", 
placement = "bottomright",
                          sbLengthPct = 0.3, sbHeightvsWidth = 1/14)
 addParams = modifyList(addParamsDefaults, addParams)

 range_x = max(spatial_obj[[addParams[["xname"]]]]) - 
min(spatial_obj[[addParams[["xname"]]]])
 range_y = max(spatial_obj[[addParams[["yname"]]]]) - 
min(spatial_obj[[addParams[["yname"]]]])
 lengthScalebar = addParams[["sbLengthPct"]] * range_x
 ## OPTION: use pretty() instead
 widthBin = makeNiceNumber(lengthScalebar / addParams[["noBins"]])
 heightBin = lengthScalebar * addParams[["sbHeightvsWidth"]]
 lowerLeftCornerScaleBar = c(x = max(spatial_obj[[addParams[["xname"]]]]) - 
(widthBin * addParams[["noBins"]]),
                             y = min(spatial_obj[[addParams[["yname"]]]]))

 scaleBarPolygon = do.call("rbind", lapply(0:(addParams[["noBins"]] - 1), 
function(n) {
   dum = data.frame(createBoxPolygon(lowerLeftCornerScaleBar + c((n * 
widthBin), 0), widthBin, heightBin))
   if(!(n + 1) %% 2 == 0) dum$cat = "odd" else dum$cat = "even"
   return(dum)
 }))
 scaleBarPolygon[[attribute]] = min(spatial_obj[[attribute]])
 textScaleBar = data.frame(x = 
lowerLeftCornerScaleBar[[addParams[["xname"]]]] + 
(c(0:(addParams[["noBins"]])) * widthBin),
                           y = 
lowerLeftCornerScaleBar[[addParams[["yname"]]]],
                           label = as.character(0:(addParams[["noBins"]]) * 
widthBin))
 textScaleBar[[attribute]] = min(spatial_obj[[attribute]])

 return(ggplot_obj +
   geom_polygon(data = subset(scaleBarPolygon, cat == "odd"), fill = 
"black", color = "black", legend = FALSE) +
   geom_polygon(data = subset(scaleBarPolygon, cat == "even"), fill = 
"white", color = "black", legend = FALSE) +
   geom_text(aes(label = label), color = "black", size = 6, data = 
textScaleBar, hjust = 0.5, vjust = 1.2, legend = FALSE))
}

library(ggplot2)
library(sp)

data(meuse)
data(meuse.grid)
ggobj = ggplot(aes(x = x, y = y, color = zinc), data = meuse) + geom_point()
# Make sure to increase the graphic device a bit
addScaleBar(ggobj, meuse, "zinc", addParams = list(noBins = 5))


On 11/18/2010 09:12 PM, Paul Hiemstra wrote:

Dear list,

A common addition to any spatial plot are a north arrow and a scale bar. 
I've searched online for a straightforward way to add those to a ggplot 
plot. I then decided to give a go myself. A crude first attempt for an 
automatic scalebar addition function is listed below. The example works for 
the meuse dataset, but a second with a different dataset did yield good 
results.

My question to you is: is there anyone who has some good tips / example 
code to add a north arrow and a scalebar to a ggplot image. Any expansions 
on the code below are also welcome.

cheers,
Paul

ps Some info on my system is listed at the very bottom

library(sp)
library(ggplot2)

data(meuse)
data(meuse.grid)

string.length = function(s) {
#  browser()
  if(!is.character(s)) s = as.character(s)
  length(strsplit(s, "")[[1]])
}

makeNiceNumber = function(num, num.pretty = 1) {
  noNumbers = string.length(as.character(round(num)))
  return(round(num / 10^(noNumbers - num.pretty)) * 10^(noNumbers - 
num.pretty))
}

makeScaleBar = function(obj, plotname, xname = "x", yname = "y", unit = 
"m", placement = "bottomright") {
#     browser()
  range_x = max(obj[[xname]]) - min(obj[[xname]])
  range_y = max(obj[[yname]]) - min(obj[[yname]])
  if(placement == "bottomright") {
    xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.05 *range_x ), 
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * 
range_x)))
    xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ), 
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * 
range_x)))
    ycoor = min(obj[[yname]]) + (0.05 * range_y)
  } else {
    xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.95 *range_x ), 
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * 
range_x)))
    xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ), 
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * 
range_x)))
    ycoor = min(obj[[yname]]) + (0.95 * range_y)
  }
  scalebar.data = data.frame(x = c(xcoor.max, xcoor.min), y = ycoor, lbl = 
c(paste(xcoor.max - xcoor.min, unit), 0))
  scalebar.data[[plotname]] = min(obj[[plotname]])
  return(list(geom_path(aes(x = x, y = y), data = scalebar.data, lwd = 2, 
color = "black"),
          geom_text(aes(x = x, y = y, label = lbl), data = scalebar.data, 
vjust = 1.3)))
}

sb = makeScaleBar(meuse.grid, "dist", placement = "topright")
ggplot(aes(x  = x, y = y, fill = dist), data = meuse.grid) + geom_tile() + 
sb[[1]] + sb[[2]]

R version 2.12.0 (2010-10-15)
Platform: i486-pc-linux-gnu (32-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=C              LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods
[8] base

other attached packages:
[1] ggplot2_0.8.7 digest_0.4.2  reshape_0.8.3 plyr_0.1.9    proto_0.3-8
[6] sp_0.9-62

loaded via a namespace (and not attached):
[1] lattice_0.19-13

hiemstra at fg-113:~$ uname -a
Linux fg-113 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC 2010 
i686 GNU/Linux

On Wed, 15 Dec 2010, Paul Hiemstra wrote:

Hi people,

I posted a similar question to the ggplot2 mailing list and with 
their help and a lot of tinkering I got a well working function to 
add a scalebar to a ggplot plot. I could add the function to automap, 
but is there another package which would be more appropraite, e.g. sp 
(Roger?)?

Paul,

If it was added to sp, sp would depend on ggplot2 and its 
dependencies, which are quite extensive, and include a circularity, 
because ggplot2 suggests maptools, which in turn depends on sp. 
Consequently, sp is not a good idea. It might even make sense to split 
sp into sp with just classes and methods, and spViz for vizualisation 
methods, but changing things now is a bit late!

It will be cleaner to try to establish the mapping functionality that 
uses ggplot2 and sp as a separate package. Maybe Hadley would see this 
as a sensible development. 

There are already two supplements to ggplot2 on R-forge, but both 
moribund, I think, which suggests that this needs thinking through.

Roger

cheers,
Paul

ps: new version of code here:

makeNiceNumber = function(num, num.pretty = 1) {
 # Rounding provided by code from Maarten Plieger
 return((round(num/10^(round(log10(num))-1))*(10^(round(log10(num))-1)))) 

}

createBoxPolygon = function(llcorner, width, height) {
 relativeCoords = data.frame(c(0, 0, width, width, 0), c(0, height, 
height, 0, 0))
 names(relativeCoords) = names(llcorner)
 return(t(apply(relativeCoords, 1, function(x) llcorner + x)))
}

addScaleBar = function(ggplot_obj, spatial_obj, attribute, addParams 
= list()) {
 addParamsDefaults = list(noBins = 5, xname = "x", yname = "y", unit 
= "m", placement = "bottomright",
                          sbLengthPct = 0.3, sbHeightvsWidth = 1/14)
 addParams = modifyList(addParamsDefaults, addParams)

 range_x = max(spatial_obj[[addParams[["xname"]]]]) - 
min(spatial_obj[[addParams[["xname"]]]])
 range_y = max(spatial_obj[[addParams[["yname"]]]]) - 
min(spatial_obj[[addParams[["yname"]]]])
 lengthScalebar = addParams[["sbLengthPct"]] * range_x
 ## OPTION: use pretty() instead
 widthBin = makeNiceNumber(lengthScalebar / addParams[["noBins"]])
 heightBin = lengthScalebar * addParams[["sbHeightvsWidth"]]
 lowerLeftCornerScaleBar = c(x = 
max(spatial_obj[[addParams[["xname"]]]]) - (widthBin * 
addParams[["noBins"]]),
                             y = 
min(spatial_obj[[addParams[["yname"]]]]))

 scaleBarPolygon = do.call("rbind", lapply(0:(addParams[["noBins"]] - 
1), function(n) {
   dum = data.frame(createBoxPolygon(lowerLeftCornerScaleBar + c((n * 
widthBin), 0), widthBin, heightBin))
   if(!(n + 1) %% 2 == 0) dum$cat = "odd" else dum$cat = "even"
   return(dum)
 }))
 scaleBarPolygon[[attribute]] = min(spatial_obj[[attribute]])
 textScaleBar = data.frame(x = 
lowerLeftCornerScaleBar[[addParams[["xname"]]]] + 
(c(0:(addParams[["noBins"]])) * widthBin),
                           y = 
lowerLeftCornerScaleBar[[addParams[["yname"]]]],
                           label = 
as.character(0:(addParams[["noBins"]]) * widthBin))
 textScaleBar[[attribute]] = min(spatial_obj[[attribute]])

 return(ggplot_obj +
   geom_polygon(data = subset(scaleBarPolygon, cat == "odd"), fill = 
"black", color = "black", legend = FALSE) +
   geom_polygon(data = subset(scaleBarPolygon, cat == "even"), fill = 
"white", color = "black", legend = FALSE) +
   geom_text(aes(label = label), color = "black", size = 6, data = 
textScaleBar, hjust = 0.5, vjust = 1.2, legend = FALSE))
}

library(ggplot2)
library(sp)

data(meuse)
data(meuse.grid)
ggobj = ggplot(aes(x = x, y = y, color = zinc), data = meuse) + 
geom_point()
# Make sure to increase the graphic device a bit
addScaleBar(ggobj, meuse, "zinc", addParams = list(noBins = 5))


On 11/18/2010 09:12 PM, Paul Hiemstra wrote:

Dear list,

A common addition to any spatial plot are a north arrow and a scale 
bar. I've searched online for a straightforward way to add those to 
a ggplot plot. I then decided to give a go myself. A crude first 
attempt for an automatic scalebar addition function is listed below. 
The example works for the meuse dataset, but a second with a 
different dataset did yield good results.

My question to you is: is there anyone who has some good tips / 
example code to add a north arrow and a scalebar to a ggplot image. 
Any expansions on the code below are also welcome.

cheers,
Paul

ps Some info on my system is listed at the very bottom

library(sp)
library(ggplot2)

data(meuse)
data(meuse.grid)

string.length = function(s) {
#  browser()
  if(!is.character(s)) s = as.character(s)
  length(strsplit(s, "")[[1]])
}

makeNiceNumber = function(num, num.pretty = 1) {
  noNumbers = string.length(as.character(round(num)))
  return(round(num / 10^(noNumbers - num.pretty)) * 10^(noNumbers - 
num.pretty))
}

makeScaleBar = function(obj, plotname, xname = "x", yname = "y", 
unit = "m", placement = "bottomright") {
#     browser()
  range_x = max(obj[[xname]]) - min(obj[[xname]])
  range_y = max(obj[[yname]]) - min(obj[[yname]])
  if(placement == "bottomright") {
    xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.05 *range_x ), 
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * 
range_x)))
    xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ), 
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * 
range_x)))
    ycoor = min(obj[[yname]]) + (0.05 * range_y)
  } else {
    xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.95 *range_x ), 
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * 
range_x)))
    xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ), 
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * 
range_x)))
    ycoor = min(obj[[yname]]) + (0.95 * range_y)
  }
  scalebar.data = data.frame(x = c(xcoor.max, xcoor.min), y = ycoor, 
lbl = c(paste(xcoor.max - xcoor.min, unit), 0))
  scalebar.data[[plotname]] = min(obj[[plotname]])
  return(list(geom_path(aes(x = x, y = y), data = scalebar.data, lwd 
= 2, color = "black"),
          geom_text(aes(x = x, y = y, label = lbl), data = 
scalebar.data, vjust = 1.3)))
}

sb = makeScaleBar(meuse.grid, "dist", placement = "topright")
ggplot(aes(x  = x, y = y, fill = dist), data = meuse.grid) + 
geom_tile() + sb[[1]] + sb[[2]]

R version 2.12.0 (2010-10-15)
Platform: i486-pc-linux-gnu (32-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=C              LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods
[8] base

other attached packages:
[1] ggplot2_0.8.7 digest_0.4.2  reshape_0.8.3 plyr_0.1.9    proto_0.3-8
[6] sp_0.9-62

loaded via a namespace (and not attached):
[1] lattice_0.19-13

hiemstra at fg-113:~$ uname -a
Linux fg-113 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 
UTC 2010 i686 GNU/Linux

Hi people,

I posted a similar question to the ggplot2 mailing list and with their help and a lot of tinkering I got a well working function to add a scalebar to a ggplot plot. I could add the function to automap, but is there another package which would be more appropraite, e.g. sp (Roger?)?

cheers,
Paul

ps: new version of code here:

makeNiceNumber = function(num, num.pretty = 1) {
 ?# Rounding provided by code from Maarten Plieger
 ?return((round(num/10^(round(log10(num))-1))*(10^(round(log10(num))-1))))
}

createBoxPolygon = function(llcorner, width, height) {
 ?relativeCoords = data.frame(c(0, 0, width, width, 0), c(0, height, height, 0, 0))
 ?names(relativeCoords) = names(llcorner)
 ?return(t(apply(relativeCoords, 1, function(x) llcorner + x)))
}

addScaleBar = function(ggplot_obj, spatial_obj, attribute, addParams = list()) {
 ?addParamsDefaults = list(noBins = 5, xname = "x", yname = "y", unit = "m", placement = "bottomright",
 ? ? ? ? ? ? ? ? ? ? ? ? ? sbLengthPct = 0.3, sbHeightvsWidth = 1/14)
 ?addParams = modifyList(addParamsDefaults, addParams)

 ?range_x = max(spatial_obj[[addParams[["xname"]]]]) - min(spatial_obj[[addParams[["xname"]]]])
 ?range_y = max(spatial_obj[[addParams[["yname"]]]]) - min(spatial_obj[[addParams[["yname"]]]])
 ?lengthScalebar = addParams[["sbLengthPct"]] * range_x
 ?## OPTION: use pretty() instead
 ?widthBin = makeNiceNumber(lengthScalebar / addParams[["noBins"]])
 ?heightBin = lengthScalebar * addParams[["sbHeightvsWidth"]]
 ?lowerLeftCornerScaleBar = c(x = max(spatial_obj[[addParams[["xname"]]]]) - (widthBin * addParams[["noBins"]]),
 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?y = min(spatial_obj[[addParams[["yname"]]]]))

 ?scaleBarPolygon = do.call("rbind", lapply(0:(addParams[["noBins"]] - 1), function(n) {
 ? ?dum = data.frame(createBoxPolygon(lowerLeftCornerScaleBar + c((n * widthBin), 0), widthBin, heightBin))
 ? ?if(!(n + 1) %% 2 == 0) dum$cat = "odd" else dum$cat = "even"
 ? ?return(dum)
 ?}))
 ?scaleBarPolygon[[attribute]] = min(spatial_obj[[attribute]])
 ?textScaleBar = data.frame(x = lowerLeftCornerScaleBar[[addParams[["xname"]]]] + (c(0:(addParams[["noBins"]])) * widthBin),
 ? ? ? ? ? ? ? ? ? ? ? ? ? ?y = lowerLeftCornerScaleBar[[addParams[["yname"]]]],
 ? ? ? ? ? ? ? ? ? ? ? ? ? ?label = as.character(0:(addParams[["noBins"]]) * widthBin))
 ?textScaleBar[[attribute]] = min(spatial_obj[[attribute]])

 ?return(ggplot_obj +
 ? ?geom_polygon(data = subset(scaleBarPolygon, cat == "odd"), fill = "black", color = "black", legend = FALSE) +
 ? ?geom_polygon(data = subset(scaleBarPolygon, cat == "even"), fill = "white", color = "black", legend = FALSE) +
 ? ?geom_text(aes(label = label), color = "black", size = 6, data = textScaleBar, hjust = 0.5, vjust = 1.2, legend = FALSE))
}

library(ggplot2)
library(sp)

data(meuse)
data(meuse.grid)
ggobj = ggplot(aes(x = x, y = y, color = zinc), data = meuse) + geom_point()
# Make sure to increase the graphic device a bit
addScaleBar(ggobj, meuse, "zinc", addParams = list(noBins = 5))


On 11/18/2010 09:12 PM, Paul Hiemstra wrote:

Dear list,

A common addition to any spatial plot are a north arrow and a scale bar. I've searched online for a straightforward way to add those to a ggplot plot. I then decided to give a go myself. A crude first attempt for an automatic scalebar addition function is listed below. The example works for the meuse dataset, but a second with a different dataset did yield good results.

My question to you is: is there anyone who has some good tips / example code to add a north arrow and a scalebar to a ggplot image. Any expansions on the code below are also welcome.

cheers,
Paul

ps Some info on my system is listed at the very bottom

library(sp)
library(ggplot2)

data(meuse)
data(meuse.grid)

string.length = function(s) {
# ?browser()
 ?if(!is.character(s)) s = as.character(s)
 ?length(strsplit(s, "")[[1]])
}

makeNiceNumber = function(num, num.pretty = 1) {
 ?noNumbers = string.length(as.character(round(num)))
 ?return(round(num / 10^(noNumbers - num.pretty)) * 10^(noNumbers - num.pretty))
}

makeScaleBar = function(obj, plotname, xname = "x", yname = "y", unit = "m", placement = "bottomright") {
# ? ? browser()
 ?range_x = max(obj[[xname]]) - min(obj[[xname]])
 ?range_y = max(obj[[yname]]) - min(obj[[yname]])
 ?if(placement == "bottomright") {
 ? ?xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.05 *range_x ), string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * range_x)))
 ? ?xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ), string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * range_x)))
 ? ?ycoor = min(obj[[yname]]) + (0.05 * range_y)
 ?} else {
 ? ?xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.95 *range_x ), string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * range_x)))
 ? ?xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ), string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * range_x)))
 ? ?ycoor = min(obj[[yname]]) + (0.95 * range_y)
 ?}
 ?scalebar.data = data.frame(x = c(xcoor.max, xcoor.min), y = ycoor, lbl = c(paste(xcoor.max - xcoor.min, unit), 0))
 ?scalebar.data[[plotname]] = min(obj[[plotname]])
 ?return(list(geom_path(aes(x = x, y = y), data = scalebar.data, lwd = 2, color = "black"),
 ? ? ? ? ?geom_text(aes(x = x, y = y, label = lbl), data = scalebar.data, vjust = 1.3)))
}

sb = makeScaleBar(meuse.grid, "dist", placement = "topright")
ggplot(aes(x ?= x, y = y, fill = dist), data = meuse.grid) + geom_tile() + sb[[1]] + sb[[2]]

R version 2.12.0 (2010-10-15)
Platform: i486-pc-linux-gnu (32-bit)

locale:
?[1] LC_CTYPE=en_US.UTF-8 ? ? ? LC_NUMERIC=C
?[3] LC_TIME=en_US.UTF-8 ? ? ? ?LC_COLLATE=en_US.UTF-8
?[5] LC_MONETARY=C ? ? ? ? ? ? ?LC_MESSAGES=en_US.UTF-8
?[7] LC_PAPER=en_US.UTF-8 ? ? ? LC_NAME=C
?[9] LC_ADDRESS=C ? ? ? ? ? ? ? LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] grid ? ? ?stats ? ? graphics ?grDevices utils ? ? datasets ?methods
[8] base

other attached packages:
[1] ggplot2_0.8.7 digest_0.4.2 ?reshape_0.8.3 plyr_0.1.9 ? ?proto_0.3-8
[6] sp_0.9-62

loaded via a namespace (and not attached):
[1] lattice_0.19-13

hiemstra at fg-113:~$ uname -a
Linux fg-113 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC 2010 i686 GNU/Linux




--
Paul Hiemstra, MSc
Department of Physical Geography
Faculty of Geosciences
University of Utrecht
Heidelberglaan 2
P.O. Box 80.115
3508 TC Utrecht
Phone: ?+3130 253 5773
http://intamap.geo.uu.nl/~paul
http://nl.linkedin.com/pub/paul-hiemstra/20/30b/770

currently @ KNMI
paul.hiemstra_AT_knmi.nl

I have a student who is interested in working on more spatial features
for ggplot2 this summer. That work is likely to involve separating out
all spatial features from ggplot2 into their own package and that
would be a good place for this.

Hadley

On Wednesday, December 15, 2010, Paul Hiemstra <p.hiemstra at geo.uu.nl> wrote:

Hi people,

I posted a similar question to the ggplot2 mailing list and with their help and a lot of tinkering I got a well working function to add a scalebar to a ggplot plot. I could add the function to automap, but is there another package which would be more appropraite, e.g. sp (Roger?)?

cheers,
Paul

ps: new version of code here:

makeNiceNumber = function(num, num.pretty = 1) {
  # Rounding provided by code from Maarten Plieger
  return((round(num/10^(round(log10(num))-1))*(10^(round(log10(num))-1))))
}

createBoxPolygon = function(llcorner, width, height) {
  relativeCoords = data.frame(c(0, 0, width, width, 0), c(0, height, height, 0, 0))
  names(relativeCoords) = names(llcorner)
  return(t(apply(relativeCoords, 1, function(x) llcorner + x)))
}

addScaleBar = function(ggplot_obj, spatial_obj, attribute, addParams = list()) {
  addParamsDefaults = list(noBins = 5, xname = "x", yname = "y", unit = "m", placement = "bottomright",
                           sbLengthPct = 0.3, sbHeightvsWidth = 1/14)
  addParams = modifyList(addParamsDefaults, addParams)

  range_x = max(spatial_obj[[addParams[["xname"]]]]) - min(spatial_obj[[addParams[["xname"]]]])
  range_y = max(spatial_obj[[addParams[["yname"]]]]) - min(spatial_obj[[addParams[["yname"]]]])
  lengthScalebar = addParams[["sbLengthPct"]] * range_x
  ## OPTION: use pretty() instead
  widthBin = makeNiceNumber(lengthScalebar / addParams[["noBins"]])
  heightBin = lengthScalebar * addParams[["sbHeightvsWidth"]]
  lowerLeftCornerScaleBar = c(x = max(spatial_obj[[addParams[["xname"]]]]) - (widthBin * addParams[["noBins"]]),
                              y = min(spatial_obj[[addParams[["yname"]]]]))

  scaleBarPolygon = do.call("rbind", lapply(0:(addParams[["noBins"]] - 1), function(n) {
    dum = data.frame(createBoxPolygon(lowerLeftCornerScaleBar + c((n * widthBin), 0), widthBin, heightBin))
    if(!(n + 1) %% 2 == 0) dum$cat = "odd" else dum$cat = "even"
    return(dum)
  }))
  scaleBarPolygon[[attribute]] = min(spatial_obj[[attribute]])
  textScaleBar = data.frame(x = lowerLeftCornerScaleBar[[addParams[["xname"]]]] + (c(0:(addParams[["noBins"]])) * widthBin),
                            y = lowerLeftCornerScaleBar[[addParams[["yname"]]]],
                            label = as.character(0:(addParams[["noBins"]]) * widthBin))
  textScaleBar[[attribute]] = min(spatial_obj[[attribute]])

  return(ggplot_obj +
    geom_polygon(data = subset(scaleBarPolygon, cat == "odd"), fill = "black", color = "black", legend = FALSE) +
    geom_polygon(data = subset(scaleBarPolygon, cat == "even"), fill = "white", color = "black", legend = FALSE) +
    geom_text(aes(label = label), color = "black", size = 6, data = textScaleBar, hjust = 0.5, vjust = 1.2, legend = FALSE))
}

library(ggplot2)
library(sp)

data(meuse)
data(meuse.grid)
ggobj = ggplot(aes(x = x, y = y, color = zinc), data = meuse) + geom_point()
# Make sure to increase the graphic device a bit
addScaleBar(ggobj, meuse, "zinc", addParams = list(noBins = 5))


On 11/18/2010 09:12 PM, Paul Hiemstra wrote:

Dear list,

A common addition to any spatial plot are a north arrow and a scale bar. I've searched online for a straightforward way to add those to a ggplot plot. I then decided to give a go myself. A crude first attempt for an automatic scalebar addition function is listed below. The example works for the meuse dataset, but a second with a different dataset did yield good results.

My question to you is: is there anyone who has some good tips / example code to add a north arrow and a scalebar to a ggplot image. Any expansions on the code below are also welcome.

cheers,
Paul

ps Some info on my system is listed at the very bottom

library(sp)
library(ggplot2)

data(meuse)
data(meuse.grid)

string.length = function(s) {
#  browser()
  if(!is.character(s)) s = as.character(s)
  length(strsplit(s, "")[[1]])
}

makeNiceNumber = function(num, num.pretty = 1) {
  noNumbers = string.length(as.character(round(num)))
  return(round(num / 10^(noNumbers - num.pretty)) * 10^(noNumbers - num.pretty))
}

makeScaleBar = function(obj, plotname, xname = "x", yname = "y", unit = "m", placement = "bottomright") {
#     browser()
  range_x = max(obj[[xname]]) - min(obj[[xname]])
  range_y = max(obj[[yname]]) - min(obj[[yname]])
  if(placement == "bottomright") {
    xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.05 *range_x ), string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * range_x)))
    xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ), string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * range_x)))
    ycoor = min(obj[[yname]]) + (0.05 * range_y)
  } else {
    xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.95 *range_x ), string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * range_x)))
    xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ), string.length(round(max(obj[[xname]]))) - string.length(round(0.3 * range_x)))
    ycoor = min(obj[[yname]]) + (0.95 * range_y)
  }
  scalebar.data = data.frame(x = c(xcoor.max, xcoor.min), y = ycoor, lbl = c(paste(xcoor.max - xcoor.min, unit), 0))
  scalebar.data[[plotname]] = min(obj[[plotname]])
  return(list(geom_path(aes(x = x, y = y), data = scalebar.data, lwd = 2, color = "black"),
          geom_text(aes(x = x, y = y, label = lbl), data = scalebar.data, vjust = 1.3)))
}

sb = makeScaleBar(meuse.grid, "dist", placement = "topright")
ggplot(aes(x  = x, y = y, fill = dist), data = meuse.grid) + geom_tile() + sb[[1]] + sb[[2]]

R version 2.12.0 (2010-10-15)
Platform: i486-pc-linux-gnu (32-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=C              LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods
[8] base

other attached packages:
[1] ggplot2_0.8.7 digest_0.4.2  reshape_0.8.3 plyr_0.1.9    proto_0.3-8
[6] sp_0.9-62

loaded via a namespace (and not attached):
[1] lattice_0.19-13

hiemstra at fg-113:~$ uname -a
Linux fg-113 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC 2010 i686 GNU/Linux




--
Paul Hiemstra, MSc
Department of Physical Geography
Faculty of Geosciences
University of Utrecht
Heidelberglaan 2
P.O. Box 80.115
3508 TC Utrecht
Phone:  +3130 253 5773
http://intamap.geo.uu.nl/~paul
http://nl.linkedin.com/pub/paul-hiemstra/20/30b/770

currently @ KNMI
paul.hiemstra_AT_knmi.nl

On Wed, 15 Dec 2010, Paul Hiemstra wrote:

Hi people,

I posted a similar question to the ggplot2 mailing list and with their
help and a lot of tinkering I got a well working function to add a scalebar
to a ggplot plot. I could add the function to automap, but is there another
package which would be more appropraite, e.g. sp (Roger?)?

Paul,

If it was added to sp, sp would depend on ggplot2 and its dependencies,
which are quite extensive, and include a circularity, because ggplot2
suggests maptools, which in turn depends on sp. Consequently, sp is not a
good idea. It might even make sense to split sp into sp with just classes
and methods, and spViz for vizualisation methods, but changing things now is
a bit late!

It will be cleaner to try to establish the mapping functionality that uses
ggplot2 and sp as a separate package. Maybe Hadley would see this as a
sensible development. There are already two supplements to ggplot2 on
R-forge, but both moribund, I think, which suggests that this needs thinking
through.

Roger

cheers,
Paul

ps: new version of code here:

makeNiceNumber = function(num, num.pretty = 1) {
?# Rounding provided by code from Maarten Plieger
?return((round(num/10^(round(log10(num))-1))*(10^(round(log10(num))-1))))
}

createBoxPolygon = function(llcorner, width, height) {
?relativeCoords = data.frame(c(0, 0, width, width, 0), c(0, height,
height, 0, 0))
?names(relativeCoords) = names(llcorner)
?return(t(apply(relativeCoords, 1, function(x) llcorner + x)))
}

addScaleBar = function(ggplot_obj, spatial_obj, attribute, addParams =
list()) {
?addParamsDefaults = list(noBins = 5, xname = "x", yname = "y", unit =
"m", placement = "bottomright",
? ? ? ? ? ? ? ? ? ? ? ? ?sbLengthPct = 0.3, sbHeightvsWidth = 1/14)
?addParams = modifyList(addParamsDefaults, addParams)

?range_x = max(spatial_obj[[addParams[["xname"]]]]) -
min(spatial_obj[[addParams[["xname"]]]])
?range_y = max(spatial_obj[[addParams[["yname"]]]]) -
min(spatial_obj[[addParams[["yname"]]]])
?lengthScalebar = addParams[["sbLengthPct"]] * range_x
?## OPTION: use pretty() instead
?widthBin = makeNiceNumber(lengthScalebar / addParams[["noBins"]])
?heightBin = lengthScalebar * addParams[["sbHeightvsWidth"]]
?lowerLeftCornerScaleBar = c(x = max(spatial_obj[[addParams[["xname"]]]])
- (widthBin * addParams[["noBins"]]),
? ? ? ? ? ? ? ? ? ? ? ? ? ? y = min(spatial_obj[[addParams[["yname"]]]]))

?scaleBarPolygon = do.call("rbind", lapply(0:(addParams[["noBins"]] - 1),
function(n) {
? dum = data.frame(createBoxPolygon(lowerLeftCornerScaleBar + c((n *
widthBin), 0), widthBin, heightBin))
? if(!(n + 1) %% 2 == 0) dum$cat = "odd" else dum$cat = "even"
? return(dum)
?}))
?scaleBarPolygon[[attribute]] = min(spatial_obj[[attribute]])
?textScaleBar = data.frame(x =
lowerLeftCornerScaleBar[[addParams[["xname"]]]] +
(c(0:(addParams[["noBins"]])) * widthBin),
? ? ? ? ? ? ? ? ? ? ? ? ? y =
lowerLeftCornerScaleBar[[addParams[["yname"]]]],
? ? ? ? ? ? ? ? ? ? ? ? ? label = as.character(0:(addParams[["noBins"]]) *
widthBin))
?textScaleBar[[attribute]] = min(spatial_obj[[attribute]])

?return(ggplot_obj +
? geom_polygon(data = subset(scaleBarPolygon, cat == "odd"), fill =
"black", color = "black", legend = FALSE) +
? geom_polygon(data = subset(scaleBarPolygon, cat == "even"), fill =
"white", color = "black", legend = FALSE) +
? geom_text(aes(label = label), color = "black", size = 6, data =
textScaleBar, hjust = 0.5, vjust = 1.2, legend = FALSE))
}

library(ggplot2)
library(sp)

data(meuse)
data(meuse.grid)
ggobj = ggplot(aes(x = x, y = y, color = zinc), data = meuse) +
geom_point()
# Make sure to increase the graphic device a bit
addScaleBar(ggobj, meuse, "zinc", addParams = list(noBins = 5))


On 11/18/2010 09:12 PM, Paul Hiemstra wrote:

Dear list,

A common addition to any spatial plot are a north arrow and a scale bar.
I've searched online for a straightforward way to add those to a ggplot
plot. I then decided to give a go myself. A crude first attempt for an
automatic scalebar addition function is listed below. The example works for
the meuse dataset, but a second with a different dataset did yield good
results.

My question to you is: is there anyone who has some good tips / example
code to add a north arrow and a scalebar to a ggplot image. Any expansions
on the code below are also welcome.

cheers,
Paul

ps Some info on my system is listed at the very bottom

library(sp)
library(ggplot2)

data(meuse)
data(meuse.grid)

string.length = function(s) {
# ?browser()
?if(!is.character(s)) s = as.character(s)
?length(strsplit(s, "")[[1]])
}

makeNiceNumber = function(num, num.pretty = 1) {
?noNumbers = string.length(as.character(round(num)))
?return(round(num / 10^(noNumbers - num.pretty)) * 10^(noNumbers -
num.pretty))
}

makeScaleBar = function(obj, plotname, xname = "x", yname = "y", unit =
"m", placement = "bottomright") {
# ? ? browser()
?range_x = max(obj[[xname]]) - min(obj[[xname]])
?range_y = max(obj[[yname]]) - min(obj[[yname]])
?if(placement == "bottomright") {
? ?xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.05 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
? ?xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
? ?ycoor = min(obj[[yname]]) + (0.05 * range_y)
?} else {
? ?xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.95 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
? ?xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
? ?ycoor = min(obj[[yname]]) + (0.95 * range_y)
?}
?scalebar.data = data.frame(x = c(xcoor.max, xcoor.min), y = ycoor, lbl =
c(paste(xcoor.max - xcoor.min, unit), 0))
?scalebar.data[[plotname]] = min(obj[[plotname]])
?return(list(geom_path(aes(x = x, y = y), data = scalebar.data, lwd = 2,
color = "black"),
? ? ? ? ?geom_text(aes(x = x, y = y, label = lbl), data = scalebar.data,
vjust = 1.3)))
}

sb = makeScaleBar(meuse.grid, "dist", placement = "topright")
ggplot(aes(x ?= x, y = y, fill = dist), data = meuse.grid) + geom_tile()
+ sb[[1]] + sb[[2]]

R version 2.12.0 (2010-10-15)
Platform: i486-pc-linux-gnu (32-bit)

locale:
?[1] LC_CTYPE=en_US.UTF-8 ? ? ? LC_NUMERIC=C
?[3] LC_TIME=en_US.UTF-8 ? ? ? ?LC_COLLATE=en_US.UTF-8
?[5] LC_MONETARY=C ? ? ? ? ? ? ?LC_MESSAGES=en_US.UTF-8
?[7] LC_PAPER=en_US.UTF-8 ? ? ? LC_NAME=C
?[9] LC_ADDRESS=C ? ? ? ? ? ? ? LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] grid ? ? ?stats ? ? graphics ?grDevices utils ? ? datasets ?methods
[8] base

other attached packages:
[1] ggplot2_0.8.7 digest_0.4.2 ?reshape_0.8.3 plyr_0.1.9 ? ?proto_0.3-8
[6] sp_0.9-62

loaded via a namespace (and not attached):
[1] lattice_0.19-13

hiemstra at fg-113:~$ uname -a
Linux fg-113 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC
2010 i686 GNU/Linux

--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no

I'd love to see a separate, dedicated package bringing spatial
functionalities to ggplot2 - this is such a great tool. However, it
seems to me that a significant problem when using ggplot2 is the lack
of geom dedicated to raster data.

My experience is you can't really deal with big rasters using
geom_tile, it takes too much memory. I guess the development of a
geom_raster is necessary to fully mimic spplot() functionalities - no
idea how demanding an effort would that be.

Pierre

2010/12/15 Roger Bivand <Roger.Bivand at nhh.no>:

On Wed, 15 Dec 2010, Paul Hiemstra wrote:

Hi people,

I posted a similar question to the ggplot2 mailing list and with their
help and a lot of tinkering I got a well working function to add a scalebar
to a ggplot plot. I could add the function to automap, but is there another
package which would be more appropraite, e.g. sp (Roger?)?

Paul,

If it was added to sp, sp would depend on ggplot2 and its dependencies,
which are quite extensive, and include a circularity, because ggplot2
suggests maptools, which in turn depends on sp. Consequently, sp is not a
good idea. It might even make sense to split sp into sp with just classes
and methods, and spViz for vizualisation methods, but changing things now is
a bit late!

It will be cleaner to try to establish the mapping functionality that uses
ggplot2 and sp as a separate package. Maybe Hadley would see this as a
sensible development. There are already two supplements to ggplot2 on
R-forge, but both moribund, I think, which suggests that this needs thinking
through.

Roger

cheers,
Paul

ps: new version of code here:

makeNiceNumber = function(num, num.pretty = 1) {
?# Rounding provided by code from Maarten Plieger
?return((round(num/10^(round(log10(num))-1))*(10^(round(log10(num))-1))))
}

createBoxPolygon = function(llcorner, width, height) {
?relativeCoords = data.frame(c(0, 0, width, width, 0), c(0, height,
height, 0, 0))
?names(relativeCoords) = names(llcorner)
?return(t(apply(relativeCoords, 1, function(x) llcorner + x)))
}

addScaleBar = function(ggplot_obj, spatial_obj, attribute, addParams =
list()) {
?addParamsDefaults = list(noBins = 5, xname = "x", yname = "y", unit =
"m", placement = "bottomright",
? ? ? ? ? ? ? ? ? ? ? ? ?sbLengthPct = 0.3, sbHeightvsWidth = 1/14)
?addParams = modifyList(addParamsDefaults, addParams)

?range_x = max(spatial_obj[[addParams[["xname"]]]]) -
min(spatial_obj[[addParams[["xname"]]]])
?range_y = max(spatial_obj[[addParams[["yname"]]]]) -
min(spatial_obj[[addParams[["yname"]]]])
?lengthScalebar = addParams[["sbLengthPct"]] * range_x
?## OPTION: use pretty() instead
?widthBin = makeNiceNumber(lengthScalebar / addParams[["noBins"]])
?heightBin = lengthScalebar * addParams[["sbHeightvsWidth"]]
?lowerLeftCornerScaleBar = c(x = max(spatial_obj[[addParams[["xname"]]]])
- (widthBin * addParams[["noBins"]]),
? ? ? ? ? ? ? ? ? ? ? ? ? ? y = min(spatial_obj[[addParams[["yname"]]]]))

?scaleBarPolygon = do.call("rbind", lapply(0:(addParams[["noBins"]] - 1),
function(n) {
? dum = data.frame(createBoxPolygon(lowerLeftCornerScaleBar + c((n *
widthBin), 0), widthBin, heightBin))
? if(!(n + 1) %% 2 == 0) dum$cat = "odd" else dum$cat = "even"
? return(dum)
?}))
?scaleBarPolygon[[attribute]] = min(spatial_obj[[attribute]])
?textScaleBar = data.frame(x =
lowerLeftCornerScaleBar[[addParams[["xname"]]]] +
(c(0:(addParams[["noBins"]])) * widthBin),
? ? ? ? ? ? ? ? ? ? ? ? ? y =
lowerLeftCornerScaleBar[[addParams[["yname"]]]],
? ? ? ? ? ? ? ? ? ? ? ? ? label = as.character(0:(addParams[["noBins"]]) *
widthBin))
?textScaleBar[[attribute]] = min(spatial_obj[[attribute]])

?return(ggplot_obj +
? geom_polygon(data = subset(scaleBarPolygon, cat == "odd"), fill =
"black", color = "black", legend = FALSE) +
? geom_polygon(data = subset(scaleBarPolygon, cat == "even"), fill =
"white", color = "black", legend = FALSE) +
? geom_text(aes(label = label), color = "black", size = 6, data =
textScaleBar, hjust = 0.5, vjust = 1.2, legend = FALSE))
}

library(ggplot2)
library(sp)

data(meuse)
data(meuse.grid)
ggobj = ggplot(aes(x = x, y = y, color = zinc), data = meuse) +
geom_point()
# Make sure to increase the graphic device a bit
addScaleBar(ggobj, meuse, "zinc", addParams = list(noBins = 5))


On 11/18/2010 09:12 PM, Paul Hiemstra wrote:

Dear list,

A common addition to any spatial plot are a north arrow and a scale bar.
I've searched online for a straightforward way to add those to a ggplot
plot. I then decided to give a go myself. A crude first attempt for an
automatic scalebar addition function is listed below. The example works for
the meuse dataset, but a second with a different dataset did yield good
results.

My question to you is: is there anyone who has some good tips / example
code to add a north arrow and a scalebar to a ggplot image. Any expansions
on the code below are also welcome.

cheers,
Paul

ps Some info on my system is listed at the very bottom

library(sp)
library(ggplot2)

data(meuse)
data(meuse.grid)

string.length = function(s) {
# ?browser()
?if(!is.character(s)) s = as.character(s)
?length(strsplit(s, "")[[1]])
}

makeNiceNumber = function(num, num.pretty = 1) {
?noNumbers = string.length(as.character(round(num)))
?return(round(num / 10^(noNumbers - num.pretty)) * 10^(noNumbers -
num.pretty))
}

makeScaleBar = function(obj, plotname, xname = "x", yname = "y", unit =
"m", placement = "bottomright") {
# ? ? browser()
?range_x = max(obj[[xname]]) - min(obj[[xname]])
?range_y = max(obj[[yname]]) - min(obj[[yname]])
?if(placement == "bottomright") {
? ?xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.05 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
? ?xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
? ?ycoor = min(obj[[yname]]) + (0.05 * range_y)
?} else {
? ?xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.95 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
? ?xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
? ?ycoor = min(obj[[yname]]) + (0.95 * range_y)
?}
?scalebar.data = data.frame(x = c(xcoor.max, xcoor.min), y = ycoor, lbl =
c(paste(xcoor.max - xcoor.min, unit), 0))
?scalebar.data[[plotname]] = min(obj[[plotname]])
?return(list(geom_path(aes(x = x, y = y), data = scalebar.data, lwd = 2,
color = "black"),
? ? ? ? ?geom_text(aes(x = x, y = y, label = lbl), data = scalebar.data,
vjust = 1.3)))
}

sb = makeScaleBar(meuse.grid, "dist", placement = "topright")
ggplot(aes(x ?= x, y = y, fill = dist), data = meuse.grid) + geom_tile()
+ sb[[1]] + sb[[2]]

R version 2.12.0 (2010-10-15)
Platform: i486-pc-linux-gnu (32-bit)

locale:
?[1] LC_CTYPE=en_US.UTF-8 ? ? ? LC_NUMERIC=C
?[3] LC_TIME=en_US.UTF-8 ? ? ? ?LC_COLLATE=en_US.UTF-8
?[5] LC_MONETARY=C ? ? ? ? ? ? ?LC_MESSAGES=en_US.UTF-8
?[7] LC_PAPER=en_US.UTF-8 ? ? ? LC_NAME=C
?[9] LC_ADDRESS=C ? ? ? ? ? ? ? LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] grid ? ? ?stats ? ? graphics ?grDevices utils ? ? datasets ?methods
[8] base

other attached packages:
[1] ggplot2_0.8.7 digest_0.4.2 ?reshape_0.8.3 plyr_0.1.9 ? ?proto_0.3-8
[6] sp_0.9-62

loaded via a namespace (and not attached):
[1] lattice_0.19-13

hiemstra at fg-113:~$ uname -a
Linux fg-113 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC
2010 i686 GNU/Linux

--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no

This is something that I hope the student would explore over summer.

Hadley

On Wed, Dec 15, 2010 at 2:27 PM, Pierre Roudier
<pierre.roudier at gmail.com>  wrote:
   

I'd love to see a separate, dedicated package bringing spatial
functionalities to ggplot2 - this is such a great tool. However, it
seems to me that a significant problem when using ggplot2 is the lack
of geom dedicated to raster data.

My experience is you can't really deal with big rasters using
geom_tile, it takes too much memory. I guess the development of a
geom_raster is necessary to fully mimic spplot() functionalities - no
idea how demanding an effort would that be.

Pierre

2010/12/15 Roger Bivand<Roger.Bivand at nhh.no>:
     

On Wed, 15 Dec 2010, Paul Hiemstra wrote:

       

Hi people,

I posted a similar question to the ggplot2 mailing list and with their
help and a lot of tinkering I got a well working function to add a scalebar
to a ggplot plot. I could add the function to automap, but is there another
package which would be more appropraite, e.g. sp (Roger?)?
         

Paul,

If it was added to sp, sp would depend on ggplot2 and its dependencies,
which are quite extensive, and include a circularity, because ggplot2
suggests maptools, which in turn depends on sp. Consequently, sp is not a
good idea. It might even make sense to split sp into sp with just classes
and methods, and spViz for vizualisation methods, but changing things now is
a bit late!

It will be cleaner to try to establish the mapping functionality that uses
ggplot2 and sp as a separate package. Maybe Hadley would see this as a
sensible development. There are already two supplements to ggplot2 on
R-forge, but both moribund, I think, which suggests that this needs thinking
through.

Roger

       

cheers,
Paul

ps: new version of code here:

makeNiceNumber = function(num, num.pretty = 1) {
  # Rounding provided by code from Maarten Plieger
  return((round(num/10^(round(log10(num))-1))*(10^(round(log10(num))-1))))
}

createBoxPolygon = function(llcorner, width, height) {
  relativeCoords = data.frame(c(0, 0, width, width, 0), c(0, height,
height, 0, 0))
  names(relativeCoords) = names(llcorner)
  return(t(apply(relativeCoords, 1, function(x) llcorner + x)))
}

addScaleBar = function(ggplot_obj, spatial_obj, attribute, addParams =
list()) {
  addParamsDefaults = list(noBins = 5, xname = "x", yname = "y", unit =
"m", placement = "bottomright",
                          sbLengthPct = 0.3, sbHeightvsWidth = 1/14)
  addParams = modifyList(addParamsDefaults, addParams)

  range_x = max(spatial_obj[[addParams[["xname"]]]]) -
min(spatial_obj[[addParams[["xname"]]]])
  range_y = max(spatial_obj[[addParams[["yname"]]]]) -
min(spatial_obj[[addParams[["yname"]]]])
  lengthScalebar = addParams[["sbLengthPct"]] * range_x
  ## OPTION: use pretty() instead
  widthBin = makeNiceNumber(lengthScalebar / addParams[["noBins"]])
  heightBin = lengthScalebar * addParams[["sbHeightvsWidth"]]
  lowerLeftCornerScaleBar = c(x = max(spatial_obj[[addParams[["xname"]]]])
- (widthBin * addParams[["noBins"]]),
                             y = min(spatial_obj[[addParams[["yname"]]]]))

  scaleBarPolygon = do.call("rbind", lapply(0:(addParams[["noBins"]] - 1),
function(n) {
   dum = data.frame(createBoxPolygon(lowerLeftCornerScaleBar + c((n *
widthBin), 0), widthBin, heightBin))
   if(!(n + 1) %% 2 == 0) dum$cat = "odd" else dum$cat = "even"
   return(dum)
  }))
  scaleBarPolygon[[attribute]] = min(spatial_obj[[attribute]])
  textScaleBar = data.frame(x =
lowerLeftCornerScaleBar[[addParams[["xname"]]]] +
(c(0:(addParams[["noBins"]])) * widthBin),
                           y =
lowerLeftCornerScaleBar[[addParams[["yname"]]]],
                           label = as.character(0:(addParams[["noBins"]]) *
widthBin))
  textScaleBar[[attribute]] = min(spatial_obj[[attribute]])

  return(ggplot_obj +
   geom_polygon(data = subset(scaleBarPolygon, cat == "odd"), fill =
"black", color = "black", legend = FALSE) +
   geom_polygon(data = subset(scaleBarPolygon, cat == "even"), fill =
"white", color = "black", legend = FALSE) +
   geom_text(aes(label = label), color = "black", size = 6, data =
textScaleBar, hjust = 0.5, vjust = 1.2, legend = FALSE))
}

library(ggplot2)
library(sp)

data(meuse)
data(meuse.grid)
ggobj = ggplot(aes(x = x, y = y, color = zinc), data = meuse) +
geom_point()
# Make sure to increase the graphic device a bit
addScaleBar(ggobj, meuse, "zinc", addParams = list(noBins = 5))


On 11/18/2010 09:12 PM, Paul Hiemstra wrote:
         

Dear list,

A common addition to any spatial plot are a north arrow and a scale bar.
I've searched online for a straightforward way to add those to a ggplot
plot. I then decided to give a go myself. A crude first attempt for an
automatic scalebar addition function is listed below. The example works for
the meuse dataset, but a second with a different dataset did yield good
results.

My question to you is: is there anyone who has some good tips / example
code to add a north arrow and a scalebar to a ggplot image. Any expansions
on the code below are also welcome.

cheers,
Paul

ps Some info on my system is listed at the very bottom

library(sp)
library(ggplot2)

data(meuse)
data(meuse.grid)

string.length = function(s) {
#  browser()
  if(!is.character(s)) s = as.character(s)
  length(strsplit(s, "")[[1]])
}

makeNiceNumber = function(num, num.pretty = 1) {
  noNumbers = string.length(as.character(round(num)))
  return(round(num / 10^(noNumbers - num.pretty)) * 10^(noNumbers -
num.pretty))
}

makeScaleBar = function(obj, plotname, xname = "x", yname = "y", unit =
"m", placement = "bottomright") {
#     browser()
  range_x = max(obj[[xname]]) - min(obj[[xname]])
  range_y = max(obj[[yname]]) - min(obj[[yname]])
  if(placement == "bottomright") {
    xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.05 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
    xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
    ycoor = min(obj[[yname]]) + (0.05 * range_y)
  } else {
    xcoor.min = makeNiceNumber(max(obj[[xname]]) - (0.95 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
    xcoor.max = makeNiceNumber(max(obj[[xname]]) - (0.5 *range_x ),
string.length(round(max(obj[[xname]]))) - string.length(round(0.3 *
range_x)))
    ycoor = min(obj[[yname]]) + (0.95 * range_y)
  }
  scalebar.data = data.frame(x = c(xcoor.max, xcoor.min), y = ycoor, lbl =
c(paste(xcoor.max - xcoor.min, unit), 0))
  scalebar.data[[plotname]] = min(obj[[plotname]])
  return(list(geom_path(aes(x = x, y = y), data = scalebar.data, lwd = 2,
color = "black"),
          geom_text(aes(x = x, y = y, label = lbl), data = scalebar.data,
vjust = 1.3)))
}

sb = makeScaleBar(meuse.grid, "dist", placement = "topright")
ggplot(aes(x  = x, y = y, fill = dist), data = meuse.grid) + geom_tile()
+ sb[[1]] + sb[[2]]

R version 2.12.0 (2010-10-15)
Platform: i486-pc-linux-gnu (32-bit)

locale:
  [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
  [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
  [5] LC_MONETARY=C              LC_MESSAGES=en_US.UTF-8
  [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
  [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods
[8] base

other attached packages:
[1] ggplot2_0.8.7 digest_0.4.2  reshape_0.8.3 plyr_0.1.9    proto_0.3-8
[6] sp_0.9-62

loaded via a namespace (and not attached):
[1] lattice_0.19-13

hiemstra at fg-113:~$ uname -a
Linux fg-113 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC
2010 i686 GNU/Linux

           

--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no