Hi all, I have posted similar questions regarding this topic, but I just can't seem to get over the hump and find a straightforward way to do this. I have attached my file as a reference. Basically, the attached file is a 5 degree by 5 degree grid of the the world (2592 cells), most of them are NA's. I just want to be able to plot this grid over a world map and color code the cells. For example, if a cell has a temperature less than 20 degrees it will be blue, 21 to 50 green color, 51-70 orange, 71+ red colored cells. For any NAs, they should be colored white. I know how to create a map of the world using map() and add a grid to it using map.grid(), but I can't color code the cells the way I need. Is there a way to do this in R? Thanks again. dxc13 http://www.nabble.com/file/p23514804/time1test.txt time1test.txt -- View this message in context: http://www.nabble.com/plotting-a-grid-with-color-on-a-map-tp23514804p23514804.html Sent from the R help mailing list archive at Nabble.com.
dxc13 wrote:> Hi all, > I have posted similar questions regarding this topic, but I just can't seem > to get over the hump and find a straightforward way to do this. I have > attached my file as a reference. > Basically, the attached file is a 5 degree by 5 degree grid of the the world > (2592 cells), most of them are NA's. I just want to be able to plot this > grid over a world map and color code the cells. For example, if a cell has > a temperature less than 20 degrees it will be blue, 21 to 50 green color, > 51-70 orange, 71+ red colored cells. For any NAs, they should be colored > white. > > I know how to create a map of the world using map() and add a grid to it > using map.grid(), but I can't color code the cells the way I need. Is there > a way to do this in R? > > Thanks again. > dxc13 http://www.nabble.com/file/p23514804/time1test.txt time1test.txtHow about the following, which doesn't need a grid at all? library(maps) temp <- as.matrix(read.table("time1test.txt")) xvals <- c(0, 0, 5, 5, 0) yvals <- c(0, 5, 5, 0, 0) map("world") palette(rainbow(50)) for (lat in seq(-90, 85, 5)) for (lon in seq(-180, 175, 5)) { col <- temp[(lat + 95)/5, (lon + 185)/5] if (!is.na(col)) polygon(lat + xvals, lon + yvals, col=col, border=NA) } palette("default") HTH Ray Brownrigg
dxc13 wrote:> Hi all, > I have posted similar questions regarding this topic, but I just can't seem > to get over the hump and find a straightforward way to do this. I have > attached my file as a reference. > Basically, the attached file is a 5 degree by 5 degree grid of the the world > (2592 cells), most of them are NA's. I just want to be able to plot this > grid over a world map and color code the cells. For example, if a cell has > a temperature less than 20 degrees it will be blue, 21 to 50 green color, > 51-70 orange, 71+ red colored cells. For any NAs, they should be colored > white. > > I know how to create a map of the world using map() and add a grid to it > using map.grid(), but I can't color code the cells the way I need. Is there > a way to do this in R? >Hi dxc13, This might get you started: temp1<-read.table("time1test.dat",header=TRUE) mapcol<-color.scale(as.matrix(temp1[36:1,]),c(0.5,1),c(0.5,0),c(1,0)) # have to draw the map to get the user coordinates map() # get the limits of the map maplim<-par("usr") # transform the temperatures into colors, reversing the row order color2D.matplot(temp1[36:1,],cellcolors=mapcol,axes=FALSE) # don't erase the current plot par(new=TRUE) # draw an empty plot with the appropriate axes (I think) plot(0,xlim=maplim[1:2],ylim=maplim[3:4],type="n") # add the map over the color squares map(add=TRUE) This seems a bit wonky, probably because I haven't adjusted the coordinates. Also, I'm only getting grayscale colors, even though the colors in "mapcol" aren't gray. Don't know why yet. Jim
Oops, forgot to include: library(plotrix) Jim
It was the NAs that fooled color2D.matplot. This gets your colors,
although not exactly what you want. Look at the help for color2D.matplot
to get that. I think fiddling with the x and y limits on the map() call
will get the positions right.
temp1<-read.table("time1test.dat",header=TRUE)
library(plotrix)
# reverse the row order, as color2D.matplot reverses it
color2D.matplot(temp1[36:1,],c(0.5,1),c(0.5,0),c(1,0),axes=FALSE)
# don't erase the above plot
par(new=TRUE)
# do a "ghost" plot with just the axes
plot(0,xlim=maplim[1:2],ylim=maplim[3:4],type="n")
# add the map on top in black
map(add=TRUE,col="black")
Jim