problem on converting the coordinates into interval [0, 1]?

Dear Porf. Roger,
 There are still a little problem with function  mess_up().
#Programs to read the rivers
library(sp);library(foreign);library(maptools)

rivers<- readShapeLines("e:/qiupu.shp")

#loops

lns <- slot(rivers, "lines")

new_lns <- lapply(lns, function(x)
{
 Lns <- slot(x, "Lines")
 new_Lns <- lapply(Lns, function(y)
  {
   new_crds <-* mess_up*(slot(y, "coords"))
   Line(new_crds)
  })
 Lines(new_Lns, ID=slot(x, "ID"))
})
new_rivers <- SpatialLines(new_lns)

1. #for your mess_up() - note, untried.
*#Erros: no function mess_up()*

2. #Also note that the projection will not be defined.
Actually, i have projected in ARCGIS, so the projection will be unneccessary
in R.

Thanks.





On 9/24/07, Roger Bivand <Roger.Bivand at nhh.no> wrote:

On Mon, 24 Sep 2007, zhijie zhang wrote:

Dear Roger,
 The reason for doing this is to get more general programs, which can be
used in the other similar conditions. If we can convert all the related
objects into internal [0,1], we can more easily use the intermediate

results

calculated from unit square,such as .bandwidth in kernels.

Exactly - with the original data, the units *are* general, because they
are in meters. Provided the other data is also using the same metric, this
also permits a direct interpretation of bandwidth, possibly with a
physical or biological basis. In the same sense, you can also get a
relative bandwidth from (bw / max(diff(bbox(<obj>)))), and multiply it out
again for a different context.

 I think the main problem maybe the lines object, that is qiupu.shp. The
scaling factor on the longer axis is from the guichi polygon.
#read the lines of two rivers in the guichi
rivers <- readShapeLines("e:/qiupu.shp")  #change the

coordinates??difficult

#plot(rivers,add=T)
I'm not very sure if they,especially qiupu lines, can be successfullyy
done.

Just loops of lapply(), not worse:

lns <- slot(rivers, "lines")

new_lns <- lapply(lns, function(x) {
  Lns <- slot(x, "Lines")
  new_Lns <- lapply(Lns, function(y) {
    new_crds <- mess_up(slot(y, "coords"))
    Line(new_crds)
  })
  Lines(new_Lns, ID=slot(x, "ID")
})
new_rivers <- SpatialLines(new_lns)

for your mess_up() - note, untried. Also note that the projection will not
be defined.

Roger

Thanks very much.

On 9/24/07, Roger Bivand <Roger.Bivand at nhh.no> wrote:

Dear Zhijie Zhang,

On Sun, 23 Sep 2007, zhijie zhang wrote:

Dear Roger,
 I have a problem on converting the coordinates into interval [0,1],

hoping

that you can give me a hand.

I think that you need to explain why. If it is just because the
coordinates "explode" because they are large, then simply scaling like
this:

library(rgdal)
guichi <- readOGR(".", "guichi")
plot(guichi, axes=TRUE)
bbox(guichi)
proj4string(guichi)
t1 <- paste("+proj=tmerc +lat_0=0 +lon_0=117 +k=1.000000 +x_0=0",
  "+y_0=-3348000 +a=6378140 +b=6356755.288157528 +units=km")
t2 <- spTransform(guichi, CRS(t1))
plot(t2, axes=TRUE)
bbox(t2)
#          min      max
# r1 10.148541 79.88203
# r2  0.834946 61.90978

gets down to 70 by 80, which is not such a numerical risk (if need be,

use

+units=kmi to get nautical miles, which reduces the numbers even more).

It

has the key advantage that you can always get back to the true

coordinates

by transforming back.

In the internal code, you will see that many packages guard by using

[-1,

+1] on both dimensions. In your case and if you know that you need

this,

you would have to work out the scaling factor on the longer axis, so

that

points on the shorter axis would be scaled correctly. But if you want

to

keep the dimensions' aspect, you could just shift the origin and the

units

as I show above.

Hope this helps,

Roger

 My data consist of points(cases), lines(rivers) and polygon (guichi

city),

and i want to change their coordinates into interval [0,1].  I have

put

the

data in the attachment, so that you can use it.
The following is the programs to read the data and one possible method

for

conversion:

library(sp)
library(foreign)
library(mgcv)
library(maptools)

#read the polygon containing the studied points
guichi <- readShapePoly("e:/guichi.shp")  #boundary polygons

containing

the

points
point_poly <-

getPolygonCoordsSlot(getPolygonsPolygonsSlot(getSpPpolygonsSlot(guichi)[[1]])[[1]])

#get the coordinates of guichi
#plot(point_poly,xlab="x", ylab="y",type="l")

#read the lines of two rivers in the guichi
rivers <- readShapeLines("e:/qiupu.shp")  #change the

coordinates??difficult

#plot(rivers,add=T)

#read the points of cases and controls
case_control <- read.csv("e:/casecontrol.csv",sep=",", header=TRUE)
#plot(case_control$x,case_control$y)

*#Plot the whole figure*
plot(point_poly,xlab="x", ylab="y",type="l")
plot(rivers,add=T)
points(case_control$x,case_control$y,add=T)

###################################################################################

#one of the possible methods to convert the x/y coordinates into

interval

[0,1]
*# But it seems there is a problem: it convert the x/y coordinates

into

interval [0,1], respectively.
# In my opinion, they should be expand or  shrink according to the

same

minimum/maximum value*.
st <- function(x)(x-min(x))/(max(x)-min(x))
case_control[,c(8,9)] <- data.frame(lapply(case_control[,c(6,7)],st))

###################################################################################

*Q1. The main problem is on the rivers, which has multiple lines.

There

are

difficulties for conversion.
Q2. when i convert the x/y coordinates, i'm not very sure whether i

should

use the same scale of conversion or not. *
Could you please help us to solve it?
Any suggestions/help are greatly appreciated.

--
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

--
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