legendplotr
I use plot function to plot a raster in R. The plot function adds a legend as default. However, the default legend added does not have a title. For instance I need to add the unit such as meters.
I cannot add a title to legend. How can I do it in plot function?
plot(raster, main = "text", sub = "This is elevation", lwd =5, col =my.palette, legend = T )
You cannot use mtext here, because spplot is based on the lattice package. mtext can only be used with base graphics.
R> p <- spplot(raster(volcano), scales = list(draw=T), at=cuts,
+ col.regions = palette(gray(seq(0,0.9,len=9))),
+ sp.layout= raster_layout, add=T)
R> class(p)
[1] "trellis" # -> lattice package
The lattice package makes use of the grid graphics engine, which is a low-level graphics system for R. Both packages are part of the base R distribution.
To add a text label at an arbitrary position you can use the function grid.text, e.g.
library("grid")
grid.text("XXX (m)", x=unit(0.95, "npc"), y=unit(0.50, "npc"), rot=-90)
You are not providing a reproducible code, so I made up a simple example that hopefully will allow you to tailor it to your needs.
library(raster)
r <- raster(volcano)
plot(r, legend = FALSE, col = rev(terrain.colors(4)))
legend("topright", legend = c("category 1", "category 2", "category 3", "category 4"), fill = rev(terrain.colors(4)))
Best Answer
You can add a title to the legend using
legend.argsin the call to plot the raster. E.g:The above snippet is taken from this question where you can also find a few more expansive examples of how the legend can be formatted (for the raster package): https://stackoverflow.com/questions/9436947/legend-properties-when-legend-only-t-raster-package