Arranging GGally plots with gridExtra?

Question

I'd like to arrange my ggpairs plots with arrangeGrob:

library(GGally)
library(gridExtra)

df <- structure(list(var1 = 1:5, var2 = 4:8, var3 = 6:10), .Names = c("var1", "var2", "var3"), row.names = c(NA, -5L), class = "data.frame")

p1 <- ggpairs(df, 1:3) 
p2 <- ggpairs(df, 1:2)

p <- arrangeGrob(p1, p2, ncol=2)

which results in this error:

Error in arrangeGrob(p1, p2, ncol = 2) : input must be grobs!

Is there a way to work around this problem?

Jacobjacoba

p1 and p2 are of class ggpairs which is apparently invalid class for arrangeGrob – Metapsychology

Yes, I figured that, too ;) But I was wondering if there is a way to still use gridExtra (or a different method) to arrange GGally plots. – Jacobjacoba

This is the only way I can think off... p1 <- ggplot(df, aes(var1, var2)) + geom_point(); p2 <- ggplot(df, aes(var2, var3)) + geom_point(); p3 <- ggplot(df, aes(var1, var3)) + geom_point(); p <- arrangeGrob(p1, p2, p3, ncol=3) – Metapsychology

Possible duplicate of plots generated by 'ggpair' and 'ggplot' side-by-side – Netti

@Netti How can my question be a duplicate of a question that was asked 1.5 years later?! – Jacobjacoba

Hi beetroot - it seems appropriate to direct readers to the more recent question, where there are two answers showing how it is now possible. – Netti

Answer 1

Unfortunately, I cannot see how that is possible.

First, it's not going to work with gridExtra, since arrangeGrob operates on TableGrob objects:

> ggplotGrob(qplot(1:100))
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.
TableGrob (6 x 5) "layout": 8 grobs
  z     cells       name                                 grob
1 0 (1-6,1-5) background      rect[plot.background.rect.3349]
2 3 (3-3,3-3)     axis-l absoluteGrob[GRID.absoluteGrob.3341]
3 1 (4-4,3-3)     spacer                       zeroGrob[NULL]
4 2 (3-3,4-4)      panel               gTree[GRID.gTree.3329]
5 4 (4-4,4-4)     axis-b absoluteGrob[GRID.absoluteGrob.3335]
6 5 (5-5,4-4)       xlab         text[axis.title.x.text.3343]
7 6 (3-3,2-2)       ylab         text[axis.title.y.text.3345]
8 7 (2-2,4-4)      title           text[plot.title.text.3347]

The inner representation of ggpairs object only contains methods to be called, not actual grobs:

> str(p1$plots)
List of 9
 $ : chr "ggally_diagAxis(ggally_data, ggplot2::aes(x = var1))"
 $ : chr "ggally_cor(ggally_data, ggplot2::aes(x = var2, y = var1))"
 $ : chr "ggally_cor(ggally_data, ggplot2::aes(x = var3, y = var1))"
 $ : chr "ggally_points(ggally_data, ggplot2::aes(x = var1, y = var2))"
 $ : chr "ggally_diagAxis(ggally_data, ggplot2::aes(x = var2))"
 $ : chr "ggally_cor(ggally_data, ggplot2::aes(x = var3, y = var2))"
 $ : chr "ggally_points(ggally_data, ggplot2::aes(x = var1, y = var3))"
 $ : chr "ggally_points(ggally_data, ggplot2::aes(x = var2, y = var3))"
 $ : chr "ggally_diagAxis(ggally_data, ggplot2::aes(x = var3))"

The whole work of constructing actual grobs is done by GGally:::print.ggpairs. Take a look at the source code and you will see grid.newpage() along with multiple popViewports and pushViewports. This means that even low-level grid approach (e.g. described here) is not applicable, since your grid constructions will get overwritten by GGally:::print.ggpairs.

There's always a way, of course. Modifying the source code is always an option, though I believe it's a long and difficult path for your task. I'd be happy to be proven wrong if anyone can come up with a simple workaround.

Malebranche

Answer 2

Just found an answer how to solve this using cowplot (found at https://github.com/ggobi/ggally/issues/256)

Solution:

 library(GGally)
 library(gridExtra)
 library(cowplot)

 df <- structure(list(var1 = 1:5,var2 = 4:8, var3 = 6:10), 
                      .Names = c("var1",  "var2", "var3"),
                      row.names = c(NA, -5L), class = "data.frame")

 p1 <- ggpairs(df, 1:3) 
 p2 <- ggpairs(df, 1:2)



 plot_grid(
   ggmatrix_gtable(p1),
   ggmatrix_gtable(p2),
   nrow = 2)

Copse

Answer 3

library(GGally)
library(gridExtra)
library(grid)

# reproducing initial data
df <- structure(list(var1 = 1:5, var2 = 4:8, var3 = 6:10), 
                .Names = c("var1", "var2", "var3"), 
                row.names = c(NA, -5L), class = "data.frame")
p1 <- ggpairs(df, 1:3) 
p2 <- ggpairs(df, 1:2)

# declaring new method for drawing ggmatrix objects using grid.draw
grid.draw.ggmatrix <- function(x, recording = T) print(x, gridNewPage = F)
# then making them look like grob objects
attributes(p1)$class <- c(attributes(p1)$class, "grob")
attributes(p2)$class <- c(attributes(p2)$class, "grob")

p <- arrangeGrob(p1, p2, ncol=2)
grid.newpage()
grid.draw(p)

Lorenzoloresz

Trying this method I get this error Error in UseMethod("depth") : no applicable method for 'depth' applied to an object of class "NULL" – Geometrid