Unexpected behavior using cbind with edited ggplotGrobs

Question

I've been trying to edit some plots created by ggplot2 using the functions provided by the packages grid and gridExtra. I realize that ggplot2 alone can make some really nice multifaceted plots. However, in some instances I like to create individual plots and then combine then together later on. While trying to do just that, I came across some unexpected behavior using cbind() with grid.draw() or grid.arrange() when using a ggplot2 graph that had been edited. Below is the code for an MWE:

#Load libraries
    library(ggplot2); library(gridExtra)

#Load data
    data(mtcars)

#Ggplot
    p = qplot(wt,mpg,data=mtcars,color=cyl)
    grob = ggplotGrob(p)

#Bold xlabel
    grobEdited = editGrob(grid.force(grob),gPath("xlab","GRID.text"),grep=TRUE,gp=gpar(fontface="bold"))

#Visualize
    grid.newpage()
    grid.draw(grobEdited)

It worked as expected. Now to illustrate the issue, lets cbind() two of the same edited ggplot2 graphs:

#Cbind example with edited graphs
    grid.newpage()
    grid.draw(cbind(grobEdited,grobEdited))

It didn't work as expected! Now test cbind() on the unedited graphs:

#Cbind example with grob
    grid.newpage()
    grid.draw(cbind(grob,grob))

Works as expected. I'm new to gridded figures, so is there something I'm doing wrong?

The issue is with the grid.force() call. Documentation suggests that drawing the result may not make sense in a different drawing context. Are you able to remove that part of the code? — Ryan Morton
@ryan-morton grid.force() allows the editing functions to have access to all of the grobs in the ggplot2 graph, so in this context I believe it is necessary. I guess I could manually edit the grob w/o using the editing functions (which will make thinks a lot more difficult). — user13317
Maybe try cbinding before the edit.. grobEdited = editGrob(grid.force(cbind(grob, grob)), gPath("xlab","GRID.text"), global=TRUE, grep=TRUE,gp=gpar(fontface="bold", col="red")) — user20650

user13317 user13317 · Accepted Answer · 2017-02-22T20:04:00

I'm posting an answer following the comment from @user20650. The easiest workaround is to cbind() the ggplot2 graphs before editing them using the editing functions provided by grid or gridExtra:

#Edit after cbind()                              
    grobEdited = editGrob(grid.force(cbind(grob,grob)),gPath("xlab","GRID.text"),global=TRUE,grep=TRUE,gp=gpar(fontface="bold"))

#Visualize
    grid.newpage()
    grid.draw(grobEdited)

Unexpected behavior using cbind with edited ggplotGrobs

1 Answers