R - How to change the width of a column in a gtable

Question

I am creating a gtable consisting of 3 x ggplot grobs using cbind, but I would like to make the middle column less wide than the 1st and 3rd column. How would I go about doing this?

The centre column only contains text so does not need equal width to the other columns containing charts:

library(grid)

# get ggplot grob
p4grob <- ggplotGrob(p4)
gdp4grob <- ggplotGrob(gdp4)
labels4grob <- ggplotGrob(labels4)
gt = cbind(gdp4grob, labels4grob, p4grob)


grid.newpage()
grid.draw(gt)

Many thanks!

Answer 1

Good suggestion in comments to use gridExtra. Much easier. But, as mentioned, I still had to do a couple of simple hacks to ensure the 3 x ggplots aligned properly, because grid.arrange bottom-aligns the content of a column (a bit odd and I didn't overcome this).

My resulting grid.arrange code is as-follows, and totally moves away from using extracted grobs and cbind and leaves it to gridExtra::grid.arrange()

```{r, fig.show='hide'}
library(grid)

# Prepare custom pyramid plot
g <- gridExtra::grid.arrange(NULL,
                        gdp4, 
                        labels4, 
                        p4, 
                        NULL,
                        widths = c(0.1,2,0.65,2,0.1), 
                        nrow = 1, 
                        top = textGrob(
                          'Top 10 Waste Generating Coastal Nations By Region\nPlastic Waste vs GDP Per Capita',
                          gp=gpar(col="white"),
                        ),
                        padding = unit(1, "cm")
                        )

Note that I actually created 5 columns, with the left-most and right-most columns being NULL, just because the output was cropping the numbers in the x-axis, and that was how I added a small amount of padding to the chart.

Also, obviously a few additional features used working towards the final product (e.g. don't confuse padding with padding the overall chart/grid/table because it is just padding the title).

I also ended up using cowplot to adjust the theme of the resulting variable from grid.arrange, explaining the change in appearance to blue background (and a few other alterations were done in ggplot2 prior to final product, so the change in appearance is not resulting from using grid.arrange()).

```{r fig.align="center", fig.height = 10, fig.width = 10}
# Format and output chart
g2 <- cowplot::ggdraw(g) + 
  theme(plot.background = element_rect(fill = "#172f52"),
        )

plot(g2)

Also note that I added fig.hide for the original R Markdown chunk because I couldn't stop grid.arrange() from outputting the chart, even when I was assigning it to a variable, so had to hide it via R Markdown tags, and then put the cowplot plot in a separate chunk for output.