plotting points on a map, assigning vectors to values from dataset

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
project.org] On Behalf Of David L Carlson
Sent: Saturday, September 15, 2012 1:33 PM
To: 'Neele'; r-help at r-project.org
Subject: Re: [R] plotting points on a map, assigning vectors to values
from dataset

You didn't include the data so we can't really test anything, but
you can simplify things quite a bit by replacing the pch= and bg=
lines with

pch <- c(24, 23, 22, 21)
bg <- c("grey24", "black", "grey77", "white")

map$number is a factor which means your categories default to
alphabetical order so the first category (factor code 1) is
fourfive and the second category (factor code 2) is sixseven.
The above lines take this into account.

Then replace the whole for loop (you really need to learn about
vectorization in R) with a single function call:

points(map$longitude, map$latitude, pch=pch(as.numeric(map$number)),
   col="black", bg=bg(as.numeric(map$number)), cex=1.5)

----------------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77843-4352

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
project.org] On Behalf Of Neele
Sent: Friday, September 14, 2012 12:41 PM
To: r-help at r-project.org
Subject: [R] plotting points on a map, assigning vectors to values

from

dataset

Dear everyone, as a newbie I fear I have made an easy mistake and am
just too
blind to see it. Can anyone help me seeing the (possibly) obvious?
I  have a command that creates a map of South America. In a separate
txt-file I stored data about latitude and longitude of languages, and
in a
third column values that differ from language to language. The

command

should read that file and assign the values to pch vectors (with bg

as

well,
because they are 21-24) and plot them on the map.
Now, the map is properly displayed, and the location of the pch

symbols

is
correct as well. But the actual symbols (and bg colors) do not match
the
original data in the txt-file. (e.g. a white circle should display
languages
with value "zeroone", and a black diamond those with "sixseven", but
there
are white diamonds for "zeroone". That is easy to change if I only

had

two
values, but I have four, and whatever I change it never matches the
actual
data).
I want to automatically match my values (e.g. zeroone, twothree etc.)
with
shapes from pch and background colors. That works fine in the legend,
but
not for the actual map. I guess there is something missing so that

the

command does not assign the correct vectors to the correlation rows

of

the
matrix.
I specified the pch and bg vectors and then tried (
pch=pch[[map$number[i]]], bg=bg[[map$number[i]]]), because the header
of the
column is "number", to make it read the correct column, but I guess
somewhere the link is missing.
The legend is displayed correctly, the retrieval path for the

txt.file

is
correct, and the .pdf is also created.
 I had problems because the lat/long values were read as factors and
not as
numericals at first; I changed that with gsub and it works. Do I
perhaps
have to change the values for the "number" column as well? (I put
str(map)
at the end below, it looks all right so far to me...)

I hope you understand my problem, and like I said, it is probably
something
very easy and clear. I found lots of info about point, pch, bg etc.,
but not
of how to automatically assign values to points using a data file.

I am grateful for any comment!
Best wishes,
Neele


library(maps)
library(mapdata)
map = read.delim("C:/Users/Neele/Desktop/number_of_modals.txt",
header=TRUE)

map$longitude=gsub(",",".",map$longitude)
map$longitude=as.numeric(as.character(map$longitude))

map$latitude=gsub(",",".",map$latitude)
map$latitude=as.numeric(as.character(map$latitude))

xlim = c(-85,-35)
ylim = c(-55,15)

pch = list("zeroone"=21, "twothree"=22,"fourfive"=24,"sixseven"=23)

bg =

list("zeroone"="white","twothree"="grey77","fourfive"="grey24","sixseve

n"="black")

          pdf('C:/Users/Neele/Desktop/number_of_modals.pdf',

height=8,

width=6)

          map("worldHires",xlim=xlim, ylim=ylim,cex.lab=0.5)

          map.axes()

          for (i in 1:nrow(map)) {
          points(map$longitude[i],map$latitude[i],   *until here
everything
as it should be*
          pch=pch[[map$number[i]]], *but here there seems to be

random

assigning of vector to value*
          bg=bg[[map$number[i]]],
          col="black",
          cex = 1.5)
          }
          title(main="Number of marked Modals")
          legend("bottomright",
          legend=c("0-1","2-3","4-5","6-7"),
          title="Legend",
          inset=0.05,
          pch=c(21,22,24,23),
          pt.bg=c("white","grey77","grey24","black")
          )

          dev.off()

str(map)

'data.frame':	63 obs. of  6 variables:
 $ latitude : num  -5 -9 1.5 -17 -13.1 ...
 $ longitude: num  -78 -67 -78.2 -69 -64.2 ...
 $ family   : Factor w/ 26 levels "Araucanian","Arawakan",..: 13 2 5

4

2 14
22 9 24 23 ...
 $ language : Factor w/ 63 levels "Aguaruna","Apurina",..: 1 2 3 4 5

6

7 8 9
10 ...
 $ number   : Factor w/ 4 levels "fourfive","sixseven",..: 3 1 1 3 1

3

1 4 3
1 ...
 $ X        : logi  NA NA NA NA NA NA ...

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