R – grid.arrange from gridExtras exiting with “only ‘grobs’ allowed in ‘gList'” after update

ggplot2gridextrarr-grid

I just updated R, R Studio, and a bunch of packages including ggplot2 and gridExtras on my Mac. Now gridExtras is failing in basic plotting with the error:

"only 'grobs' allowed in "gList""

Here's some code that should work but does not:

library(ggplot2)
p1 = qplot(1:10,rnorm(10))
p2 = qplot(1:10,rnorm(10))
library(gridExtra)
grid.arrange(p1, p2, ncol=2, main = "Main title")

This dumps out the following error:

Error in gList(list(grobs = list(list(x = 0.5, y = 0.5, width = 1, height = 1,  : 
  only 'grobs' allowed in "gList"
In addition: Warning message:
In grob$wrapvp <- vp : Coercing LHS to a list

Any help is appreciated!

Best Answer

It is because grid.arrange does not have a main parameter anymore (seems to have been eliminated around Summer 2015 with the 2.0.0 release) and thus thinks that the main= parameter must be a grob. To replace the main, you can use the top parameter now (as well as a bottom, left, and right).

So this works for example:

library(ggplot2)
p1 = qplot(1:10,rnorm(10))
p2 = qplot(1:10,rnorm(10))

library(gridExtra)
grid.arrange(p1, p2, ncol=2,top="Main Title")

The message is a bit confusing, that is because it looks at all the parameters it does not know and assumes they might be grobs (graphical objects) that it can plot. A confusing error message like this is the price you pay for that flexibility.

Note: - if you have a lot of grobs you should consider packing them all into a list and use the form:

grid.arrange( grobs = list(p1,p2,...),...

Here is what that above code results in:

Related Solutions

R – Save multiple ggplot2 plots as R object in list and re-displaying in grid

I can think of two solutions.

1. If your goal is to just save the list of plots as R objects, I recommend:

    saveRDS(object = pltlist, file = "file_path")

This way when you wish to reload in these graphs, you can just use readRDS(). You can then put them in cowplot or gridarrange. This command works for all lists and R Objects.

One caveat to this approach is if settings/labeling for ggplot2 is dependent upon things in the environment (not the data, but stuff like settings for point size, shape, or coloring) instead of the ggplot2 function used to make the graph), your graphs won't work until you restore your dependencies. One reason to save some dependencies is to modularize your scripts to make the graphs.

Another caveat is performance: From my experience, I found it is actually faster to read in the data and remake individual graphs than load in an RDS file of all the graphs when you have a large number of graphs (100+ graphs).

2. If your goal is to save an 'image' or 'picture' of each graph (single and/or multiplot as .png, .jpeg, etc.), and later adjust things in a grid manually outside of R such as powerpoint or photoshop, I recommend:

    filenames <- c("Filename_1", "Filename_2") #actual file names you want... 
    lapply(seq_along(pltlist), function(i) {
      ggsave(filename = filenames[i], plot = pltlist[[i]], ...) #use your settings here
    })

Settings I like for single plots:

    lapply(seq_along(pltlist), function(i) ggsave(
      plot = pltlist[[i]], 
      filename = paste0("plot_", i, "_", ".tiff"), #you can even paste in pltlist[[i]]$labels$title
      device = "tiff", width=180, height=180, units="mm", dpi=300, compression = "lzw", #compression for tiff
      path = paste0("../Blabla") #must be an existing directory.
    ))

You may want to do the manual approach if you're really OCD about the grid arrangement and you don't have too many of them to make for publications. Otherwise, when you do grid.arrange you'll want to do all the specifications there (adjusting font, increasing axis label size, custom colors, etc.), then adjust the width and height accordingly.

Best Answer

Related Solutions

R – Save multiple ggplot2 plots as R object in list and re-displaying in grid

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