Question

I have a contour plot, I am wondering is it possible to label the individual contour levels as well as the colours? (i.e. say the first pink contour is 0.2, second is 0.4 or whatever works).

Also, what is the argument for filling land as a solid color?

library(lattice)
contourplot(cor_Warra_SF_SST_SON, region=TRUE, at=seq(-1, 1, 0.2), 
labels=FALSE, row.values=lon_sst, column.values=lat_sst,
xlab='longitude', ylab='latitude')

Answer 1

To include labels for the contour lines, simply set labels = TRUE (in place of the labels=FALSE that you are currently using).

?contourplot document the labels argument thusly:

labels: typically a logical indicating whether contour lines should
be labelled, but other possibilities for more sophisticated
control exists. Details are documented in the help page for
‘panel.levelplot’, to which this argument is passed on
unchanged. That help page also documents the ‘label.style’
argument, which affects how the labels are rendered.

To add filled polygons for the continents, I’d try using mapplot() from the latticeExtra package, adding it to the plot you’re already produced using layer(), also from latticeExtra. (I can’t get much more specific than that without having access to the data you are using.)