Question

I am trying to make a temperature map, all works fine but I don’t know how to have a fixed color palette.

Actually I have this :

rgb.palette <- colorRampPalette(c("blue","green","yellow","orange","red"), 
                                space = "Lab")

image.plot(akima.smooth, 
           col = rgb.palette(NBR.COLORS), 
           main=main_title, 
           horizontal=TRUE,
           axes=TRUE)

This solution works but the colors which are painted are always from blue to red.

For example if the lowest temperature on the map is -10°C the color will be blue, but in another map if the lowest temperature is +25°C that color will be blue too.

How can I define a fixed color panel such as :

-30°C => blue
-20°C => light blue
-10°C => dark green
  0°C => green
 10°C => yellow

If in map 1 lowest temperature is -20 I want “light blue” and in map 2 if lowest temperature is 10°C I want “yellow” color.

Answer 1

I used this solution :

col = colorRampPalette(c("darkmagenta","blue","green","yellow","orange","red"),
                       space="Lab")(NBR.COLORS) 
breaks = c(seq(-35, 10, length.out=NBR.COLORS/2), 10, 
           seq(10, 35, length.out=NBR.COLORS/2))
image.plot(akima.smooth, col=col, breaks=breaks, main=main_title,
           horizontal=TRUE,axes=TRUE);