ggplot2: how to easily combine multiple graphs in one, part 2

This article will show step by step how to combine several ggplot graphs in one or several illustrations using the helper functions available in the R ggpubr , cowplot and gridExtra packages . We also describe how to export the resulting graphs to a file.

Repositioning by row or column

Using the ggpubr package

We use the nested functions of ggarrange() to change the location of the graphs in rows or columns.

For example, the code below does the following:

the scatter diagram (sp) will be in the first row and occupy two columns
scatter diagram (bxp) and scatter diagram (dp) will occupy the second row and two different columns

 ggarrange(sp, #      ggarrange(bxp, dp, ncol = 2, labels = c("B", "C")), #         nrow = 2, labels = "A" #    )

Use the cowplot package

The following combination of functions [from the cowplot package] can be used to place graphs at specific locations of a given size: ggdraw() + draw_plot() + draw_plot_label() .

ggdraw (). Initialize the blank canvas:

 ggdraw()

Note that by default, the coordinates vary from 0 to 1, and the point (0, 0) is in the lower left corner of the canvas (see illustration below).

draw_plot (). Has a schedule somewhere on the canvas:

 draw_plot(plot, x = 0, y = 0, width = 1, height = 1)

plot : plot to place (ggplot2 or gtable)
x, y : x / y coordinates of the lower left corner of the graph
width, height : the width and height of the graphic

draw_plot_label (). Adds a label in the upper right corner of the chart.

Can work with label vectors with associated coordinates.

 draw_plot_label(label, x = 0, y = 1, size = 16, ...)

label : label vector
x, y : vector with x / y coordinates of each label, respectively
size : label font size

For example, you can combine several graphs of different sizes with a specific location:

 library("cowplot") ggdraw() + draw_plot(bxp, x = 0, y = .5, width = .5, height = .5) + draw_plot(dp, x = .5, y = .5, width = .5, height = .5) + draw_plot(bp, x = 0, y = 0, width = 1, height = 0.5) + draw_plot_label(label = c("A", "B", "C"), size = 15, x = c(0, 0.5, 0), y = c(1, 1, 0.5))

Use the gridExtra package

The arrangeGrop() function [in gridExtra ] helps to change the arrangement of graphs in rows or columns.

For example, the code below does the following:

the scatter diagram (sp) will be in the first row and occupy two columns
scatter diagram (bxp) and scatter diagram (dp) will occupy the second row and two different columns

 library("gridExtra") grid.arrange(sp, #         arrangeGrob(bxp, dp, ncol = 2),#         nrow = 2) #

In grid.arrange() you can also use the layout_matrix argument to create complex relative positioning of graphs.

In the code below layout_matrix is a 2x2 matrix (2 rows and 2 columns). The first line - all units, where the first chart occupies two columns; the second line contains graphs 2 and 3, each of which occupies its own column.

 grid.arrange(bp, #      bxp, sp, #     ncol = 2, nrow = 2, layout_matrix = rbind(c(1,1), c(2,3)))

You can also add annotation to the output of grid.arrange() using the auxiliary function draw_plot_label() [in cowplot ].

To easily add annotations to the conclusions of grid.arrange() or arrangeGrob() functions grid.arrange() arrangeGrob() type), you first need to convert them to ggplot type using the as_ggplot() function [in ggpubr ]. You can then use the draw_plot_label() function [in cowplot ].

 library("gridExtra") library("cowplot") #    arrangeGrob #   gtable (gt) gt <- arrangeGrob(bp, #      bxp, sp, #     ncol = 2, nrow = 2, layout_matrix = rbind(c(1,1), c(2,3))) #      p <- as_ggplot(gt) + #   ggplot draw_plot_label(label = c("A", "B", "C"), size = 15, x = c(0, 0, 0.5), y = c(1, 0.5, 0.5)) #   p

In the code above, we used arrangeGrob() instead of grid.arrange() . The main difference between these two functions is that grid.arrange() automatically displays ordered graphs. Since we wanted to add an annotation to the graphs before drawing them, it is preferable to use the arrangeGrob() function in this case.

Use the grid package

The grid package allows you to set a complex mutual arrangement of graphs using the grid.layout() function. It also provides the viewport() helper function for specifying a region, or scope. The print() function is used to place graphs in a given region.

The steps can be described as:

Create graphics: p1, p2, p3, ....
Go to a new page using the grid.newpage() function
Create location 2X2 - number of columns = 2; number of lines = 2
Set scope: rectangular area on graphics device
Print a graph in scope

 library(grid) #     grid.newpage() #  : nrow = 3, ncol = 2 pushViewport(viewport(layout = grid.layout(nrow = 3, ncol = 2))) #        define_region <- function(row, col){ viewport(layout.pos.row = row, layout.pos.col = col) } #   print(sp, vp = define_region(row = 1, col = 1:2)) #     print(bxp, vp = define_region(row = 2, col = 1)) print(dp, vp = define_region(row = 2, col = 2)) print(bp + rremove("x.text"), vp = define_region(row = 3, col = 1:2))

Using common legends for combined ggplot graphs

To set a common legend for several ordered graphs, you can use the ggarrange() function [in ggpubr ] with these arguments:

common.legend = TRUE : make a shared legend
legend : set the position of the legend. The allowed value is one of c (“top”, “bottom”, “left”, “right”)

 ggarrange(bxp, dp, labels = c("A", "B"), common.legend = TRUE, legend = "bottom")

Scatter plot with unconditional density graphs

 #  ,    ("Species") sp <- ggscatter(iris, x = "Sepal.Length", y = "Sepal.Width", color = "Species", palette = "jco", size = 3, alpha = 0.6)+ border() #      x ( )   y ( ) xplot <- ggdensity(iris, "Sepal.Length", fill = "Species", palette = "jco") yplot <- ggdensity(iris, "Sepal.Width", fill = "Species", palette = "jco")+ rotate() #   yplot <- yplot + clean_theme() xplot <- xplot + clean_theme() #   ggarrange(xplot, NULL, sp, yplot, ncol = 2, nrow = 2, align = "hv", widths = c(2, 1), heights = c(1, 2), common.legend = TRUE)