R gridExtra: modify theme on the fly for a single tableGrob?

Question

I read Baptiste's excellent explanation of gridextra's tableGrob functions here: https://github.com/baptiste/gridextra/wiki/tableGrob

From his section on Aesthetic formatting:

tt1 <- ttheme_default()
tt2 <- ttheme_minimal()
tt3 <- ttheme_minimal(
  core=list(bg_params = list(fill = blues9[1:4], col=NA),
            fg_params=list(fontface=3)),
  colhead=list(fg_params=list(col="navyblue", fontface=4L)),
  rowhead=list(fg_params=list(col="orange", fontface=3L)))

grid.arrange(
  tableGrob(iris[1:4, 1:2], theme=tt1),
  tableGrob(iris[1:4, 1:2], theme=tt2),
  tableGrob(iris[1:4, 1:2], theme=tt3),
  nrow=1)

I wonder is it possible to modify a theme "on-the-fly" for a particular tableGrob, e.g., something like:

grid.arrange(
  tableGrob(iris[1:4, 1:2], theme=tt1 + theme_default(core=list(fg_params=list(cex=0.7))),
  tableGrob(iris[1:4, 1:2], theme=tt2),
  tableGrob(iris[1:4, 1:2], theme=tt3),
  nrow=1)

This last block of code does NOT work, but what I wanted to do was modify theme "tt1" on the fly to change the core text size JUST for the first tableGrob, WITHOUT permanently changing the theme "tt1".

Thanks!

Answer 1

Themes appear to be just lists. You can update properties of lists with modifyList. For example

grid.arrange(
  tableGrob(iris[1:4, 1:2], theme=modifyList(tt1, list(core=list(fg_params=list(cex=0.7))))),
  tableGrob(iris[1:4, 1:2], theme=tt2),
  tableGrob(iris[1:4, 1:2], theme=tt3),
  nrow=1)