Adding a color key to contour plots in R

Question

I want to create a contour plot that has a color key next to it.

I would make the contour plot like this:

data(volcano)
image(volcano)
contour(volcano, add = TRUE)

However, image() does not support a legend as far as I know. I saw that there is also a contourplot() function in the lattice package, however, I cannot figure it out how to overlay the map with the contour lines when using levelplot(volcano) and contourplot(volcano)

Ideally I want my plot to look like this but with a color key:

enter image description here

I'm sure someone has a `ggplot` solution to this, but this was also addressed in this question previously - http://stackoverflow.com/questions/13355176/gradient-legend-in-base — thelatemail, Apr 08 '13 at 01:49
3rd example from the bottom: http://docs.ggplot2.org/current/stat_contour.html — Ricardo Saporta, Apr 08 '13 at 01:52
Thanks for the comment! Hm, I wanted to avoid using ggplot2, I can't help it, but I don't like the look of the ggplot2 graphics. But if there is no other way I might have to do it this way — , Apr 08 '13 at 01:55

score 14 · Accepted Answer · answered Apr 08 '13 at 01:55

14

You could use image.plot from the fields package. This creates a legend by default.

library(fields)
image.plot(volcano)
contour(volcano, add = TRUE)

enter image description here

answered Apr 08 '13 at 01:55

mnel

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Nice, this was something I was looking for! – Apr 08 '13 at 01:56
1

Magic! Nice answer - will have to remember this one! – thelatemail Apr 08 '13 at 02:00

Adding a color key to contour plots in R

1 Answers1