Question

I am trying to plot the image of this raster file. The colour of the legend was like this: low values with red colour and high values with green.

But normally red colour is associated with high values. That’s why I then used rev to reverse the colour of the legend. However I got something different. Is there another function to reverse the colour of the legend and keep the colours as they are.

require(raster)
require(fields)
r = raster(y)
extent(r) = extent(c(xmn=-180,xmx=180,ymn=-90,ymx=90))
plot(r, col = rainbow(20, s = 1, v = 1, start = 0, 
     end = 1),lab.breaks=seq(0,0.6,0.05),
     breaks=seq(0,0.6,0.05), zlim=c(0.0,0.6),horizontal = TRUE, 
     xlab="Longitude", ylab="Latitude",legend.shrink = 0.9,
     legend.width = 1.2)

then I used this which gave me:

plot(r, col = rev(rainbow(20, s = 1, v = 1, start = 0, end = 1)),
     lab.breaks=seq(0,0.6,0.05),breaks=seq(0,0.6,0.05),
     zlim=c(0.0,0.6),horizontal = TRUE, xlab="Longitude", 
     ylab="Latitude",legend.shrink = 0.9,legend.width = 1.2)

Answer 1

Obviously you didn’t check the colors.

> length(rainbow(20, s = 1, v = 1, start = 0, end = 1))
[1] 20

But not all 20 are used, you only use 12 of them, so:

plot(r, col = rev(rainbow(20, s = 1, v = 1, start = 0, end = 1)[1:12]),
     lab.breaks=seq(0,0.6,0.05),breaks=seq(0,0.6,0.05),
     zlim=c(0.0,0.6),horizontal = TRUE, xlab="Longitude", 
     ylab="Latitude",legend.shrink = 0.9,legend.width = 1.2)

should give you the plot you want. After all, you have 13 break values, so only 12 categories. Which means you could have done:

plot(r, col = rev(rainbow(12, s = 1, v = 1, start = 0, end = 1)),
     lab.breaks=seq(0,0.6,0.05),breaks=seq(0,0.6,0.05),
     zlim=c(0.0,0.6),horizontal = TRUE, xlab="Longitude", 
     ylab="Latitude",legend.shrink = 0.9,legend.width = 1.2)