绘制两个图表出现错误：无法将 class 列表的 object 转换为 grob

Question

I am trying to place two boxplots (box1, box2) beside each other and to label them "A" and "B" in the upper left corner. I am trying to use the cowplot -package for this.

This is the function:

plot_grid(box1, box2, labels = c('A', 'B'), label_size = 12)

Then I get the warning message:

In as_grob.default(plot): Cannot convert object of class list into a grob.*

And the only printout I get is the A and B letters. I have also tried to use:

boxC <- c(box1, bow2)
plot_grid(plotlist = boxC, labels = c('A', 'B'), label_size = 12, nrow=2)

My code mostly came from the answers to this similar question, but it does not seem to work for me.

Lay out multiple ggplot graphs on a page

In that question someone also suggested using dev.off() but that did not work for me either.

So grateful for replies!

The solution that I wrote based on mhh's reply:

BOX1_data <- read.table(file = "clipboard", 
                  sep = "\t", header=TRUE)
BOX1_data$Histology <- as.factor(BOX1_data$Histology)
BOX1plot <- ggplot(BOX1_data, aes(x=Histology, y=No.Variants)) + geom_boxplot()
BOX1plot

BOX2_data <- read.table(file = "clipboard", 
                  sep = "\t", header=TRUE)
BOX2_data$Stage <- as.factor(BOX2_data$Stage)
BOX2plot <- ggplot(BOX2_data, aes(x=Stage, y=No.Variants)) + geom_boxplot()
BOX2plot

BOX_list <- list(BOX1plot, BOX2plot)
> ggarrange(plotlist = BOX_list, labels = c('A', 'B'), ncol = 2)

Answer 1

This is because it is expecting a list, but you are providing a vector, To overcome this, you can simply use boxC <- list(box1,box2) .

Here is a working example

To do this, you need ggplot2 and ggpubr Install the latter with install.packages("ggpubr") . Then get them both into your workspace with library(ggpubr)

library(ggplot2)
library(ggpubr)
df1 <- data.frame(group = "Stuff",  var = runif(10))
df2 <- data.frame(group = "Stash",  var = runif(10))

box1 <- ggplot(data = df1, aes(y = var)) +
  geom_boxplot()

box2 <- ggplot(data = df2, aes(y = var)) +
  geom_boxplot()

my_plot_list <- list(box1,box2)

ggarrange(plotlist = my_plot_list, labels = c('A', 'B'), nrow = 2)

^{Created on 2020-08-19 by the reprex package (v0.3.0)}

Answer 2

Thanks to mhh's answer I made this code which works: :)

BOX1_data <- read.table(file = "clipboard", 
                  sep = "\t", header=TRUE)
BOX1_data$Histology <- as.factor(BOX1_data$Histology)
BOX1plot <- ggplot(BOX1_data, aes(x=Histology, y=No.Variants)) + geom_boxplot()
BOX1plot

BOX2_data <- read.table(file = "clipboard", 
                  sep = "\t", header=TRUE)
BOX2_data$Stage <- as.factor(BOX2_data$Stage)
BOX2plot <- ggplot(BOX2_data, aes(x=Stage, y=No.Variants)) + geom_boxplot()
BOX2plot

BOX_list <- list(BOX1plot, BOX2plot)
> ggarrange(plotlist = BOX_list, labels = c('A', 'B'), ncol = 2)