Superimposing two plots

December 20, 2006 at 11:57 am | In GNU-R, Graphics | 2 Comments

If you want to give two plot commands, and do not want the second one to wipe out the first one, do the following.

 

plot(first plot)

 

par(new=TRUE)

 

plot(second plot)

 

This will superimpose the second plot on the first. Note that the two plots may have different scales. To ensure that they use a particular (say, same) scale, set ylim and xlim in both the graphs. If you are using the same scales, you may want to turn off axes and labels in the second plot. Otherwise, they will be printed again.

scatterplot.matrix

December 20, 2006 at 11:55 am | In GNU-R, Graphics | Leave a Comment

John Fox’s package, “car”, has a very useful scatterplot.matrix (or simply spm) to make scatterplots of pairs from a set of variables. The plot below was created using

library(“car”)
scatterplot.matrix(~Exppop+Exppphc+literacy+Oppphc, reg.line=lm, smooth=TRUE, span=0.5, diagonal = ‘density’, data=temp)
dev.print(jpeg, file=”~/graph-matrix.jpg”, width=500, height=500, pointsize=10)

graph-matrix.jpg

jitter

December 20, 2006 at 11:52 am | In GNU-R | Leave a Comment

jitter is an interesting function that adds a small noise to a vector. A very useful feature if you want to plot data points which have some ties.

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