How to edit a previous plot in an R graphics device split by mfrow

3
votes

I have an existing plotting function (perhaps written by someone else) that uses mfrow to plot multiple figures on the same graphics device. I want to edit figures that have already been plotted (e.g. perhaps add a reference line to figure 1)

par(mfrow = c(1, 2))
plot(1:10)
hist(1:10)
# Oh no!  I want to add abline(a = 0, b = 1) to the first plot!

Assume this code is nested in another plotting function PlotABunchOfStuff(1:10) that I can't modify.

I don't want to modify PlotABunchOfStuff because someone else owns it, or I'm just debugging and won't need the extra details once the bug is found.

2
rplotgraphics
Hi Steven. The above solution answered your question ? If yes, could you simply validate it. Thanks. – Rémi Coulaud
My question remains unanswered. ggplot is a completely different graphics framework. – Steven Scott
And the edit 1 ? – Rémi Coulaud

2 Answers

1
votes

Use par(mfg).

For example:

par(mfrow = c(2, 3))

for (i in 1:6) {
  plot(i, xlim = c(0,7), ylim = c(0, 7))
}

par(mfg = c(2, 2))
points(3,3,col= "red")

par(mfg = c(1, 1))
points(3,3,col= "blue")
0
votes

If you are ready to use ggplot I think you can find what you want in the code below :

df <- data.frame(x = 1:10, y = 1:10)
g1 <- ggplot(df, aes(x = x, y = y)) +
  geom_point()
g2 <- ggplot(df, aes(x = x, y = y)) +
  geom_line()

grid.arrange(g1, g2)

g1 <- g1 + geom_smooth(method='lm',formula=y~x)  # it could be anything else !

grid.arrange(g1, g2)

Edit 1

Create a graphical object in windows which will be destroye after dev.off() if filename = "" :

win.metafile(filename = "")

By default inhibit doesn't allow the plot to be recorded so we use enable :

dev.control('enable')
plot(1:10)
p <- recordPlot() 
dev.off()
replayPlot(p)

p
abline(a = 1, b = 1, col = "red")
p <- recordPlot() 
dev.off()
replayPlot(p)

My inspirations on Stackoverflow :

R plot without showing the graphic window Save a plot in an object

My inspirations on R :

https://www.rdocumentation.org/packages/grDevices/versions/3.6.0/topics/dev https://www.rdocumentation.org/packages/grDevices/versions/3.6.0/topics/recordPlot

I hope it helps you ! Good luck.