Layout function to plot multiple maps

Question

I need to arrange 4 different plots together in a specific way and I'm trying to use the layout() function, but just keep getting the wrong results.

If the code was working the way I wanted, the layout would look like this:

so the increase plot is at the top center, decrease plot is bottom center, base21 is left and base22 is right and centered vertically between the others.

Here is the code I have at this point:

layout_matrix <- matrix(c(1, 1, 1, 2, 2, 3, 3, 4, 4, 4),  ncol = 3)

# arrange plots using gridExtra and layout
grid.arrange(
  arrangeGrob(increase_map, decrease_map, nrow = 3),
  arrangeGrob(base21_map, base22_map, ncol = 3),
  layout_matrix = layout_matrix
)

but it returns this:

How can I get it to arrange like the drawing?

Answer 1

I find it is helpful to write out the layout visually as though you are looking at it, with byrow=TRUE. E.g.

layout_matrix <- matrix(
    c(0,0,0,1,1,1,1,1,0,0,0,
      2,2,2,2,2,0,3,3,3,3,3,
      0,0,0,4,4,4,4,4,0,0,0),
      nrow=3, byrow=TRUE)

Example image of how this looks using layout/layout.show in base graphics: