问题
I need to wrap several plots in a grid, often an uneven number, so there'll often be an "empty spot".
I need to use arrangeGrob() -- not grid.arrange() -- because I want to save the plot for later, not plot() it right away.
This works fine, but oddly, arrangeGrob() leaves some weird background in the empty spots.
Like so:
library(ggplot2)
p1 <- ggplot(mtcars, aes(x=factor(cyl), y=mpg)) + geom_boxplot()
p2 <- ggplot(mtcars, aes(x=factor(cyl), y=wt)) + geom_boxplot()
p3 <- ggplot(mtcars, aes(x =factor(cyl), y=disp)) + geom_boxplot()
library(gridExtra)
y <- arrangeGrob(p1, p2, p3, ncol = 2)
plot(y)
yields a plot with some weird gray stuff in the bottom right corner:
Compare this to grid.arrange():
grid.arrange(p1, p2, p3, ncol = 2)
yields a pretty plot with no grey weirdness:
Where does this gray stuff in the bottom right corner come from? And how do I get rid of it?
Notice that I cannot avoid the empty spots by changing ncol; I sometimes have an uneven number of plots, so there'll always be empty spots.
I'm ok with empty spots, I just like them to be clean.
(In isolation, that last sentence sounds pretty OCD-ish.
UPDATE
The package author (?) answered below: I should have used grid.draw(y).
A similar problem remains (maybe the same root cause?): if you plot some object before, the "empty spot" remains occupied by that past plot. Weird. Like so:
plot(p1)
grid.draw(y)
yields:
回答1:
arrangeGrob() now returns a gtable, which you should draw with grid.draw(), not plot().
grid.draw(y)
yields
To get rid of artefacts from past plots (as per above update) use grid.newpage().
回答2:
Remove the nrow argument. Like so:
library(ggplot2)
p1 <- ggplot(mtcars, aes(x=factor(cyl), y=mpg)) + geom_boxplot()
p2 <- ggplot(mtcars, aes(x=factor(cyl), y=wt)) + geom_boxplot()
library(gridExtra)
y <- arrangeGrob(p1, p2, ncol = 2)
plot(y)
来源：https://stackoverflow.com/questions/31463445/how-do-i-get-rid-of-random-background-grid-from-arrangegrob