Plotting colors on a world map
So, this would allow me to assign a color to each of the 2592 rectangular grid cells on a map of the world? I guess I am having trouble finding a suitable method of doing this. Also, to be able to distinguish country boundaries from the grid lines (which are both black color), could the grid lines be transparent so that all we see is the map of the world in various colors? I was thinking that <10 degrees would be light blue, 10-30 degrees would be blue, 31-40 be green, 41-50 be yellow, 51-60 be dark yellow, 61-70 be orange, 71-80 be red, 81-90 be dark red. Any help is appreciated in getting this task accomplished. Thanks
Duncan Murdoch-2 wrote:
On 5/11/2009 10:32 AM, dxc13 wrote:
Hi useR's I have created a simple map of the world using the following code: m <- map(xlim=c(-180,180), ylim=c(-90,90)) map.axes() I then create a grid of dimension 36x72 using the code: map.grid(m, nx=72, ny=36, labels=FALSE, col="black") This gives 2592 grid cells. In a separate data set of dimension 36x72, I have 2592 temperature values (some missing values are present) ranging from -20 degrees F to 90 degrees F. My question is, how can I create a reasonable color scheme (low temperatures in light blue to higher temperatures in dark red) and plot the temperature colors in their respective grid cells on the map? Take this data matrix as some example data: T <- sample(-10:90, 2592, replace=TRUE) mat <- matrix(T, nrow=36, ncol=72)
The colorspace package can make nice color sequences for this sort of thing, and image() can add them to a plot. In colorspace, look at the examples for diverge_hcl. Duncan Murdoch
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