Combine Plot and Table in R GGplot2

When presenting data on a plot, it is sometimes useful to also show a table with the actual numbers next to the plot. In some cases (e.g., mean profile plots and forest plots), the x-axes or y-axes of the individual plots/tables need to align with each other.

There are several methods in combine plots and tables in r. In this article we will focus only on simple methods, based on the functions grid.arrange() and ggarrange().

Combine Mean Profile Plot and Table

We will achieve this in three steps:

1. Create a mean profile plot
2. Create a table with the number of samples per time point
3. Combine plot and table

The Dataset

1. Create a Mean Profile Plot

#Mean profiles with 95% confidence interval
g1 <- ggplot(statsBG, aes(x=timedays, y=meanBG, color=groupid, shape=groupid)) +
  geom_line() +
  geom_errorbar(aes(ymin = ci95lower, ymax = ci95upper), width = 0.3) +
  geom_point(size = 3) + 
  labs(color="Group", x="Day", y = "Mean Fasting Blood Glucose (mg/dl)") +
  scale_x_continuous(breaks=seq(1,10,1), limits = c(0.5,10.5)) +
  ylim(110, 180) + 
  #specify "Group" to avoid creating separate legends
  scale_color_manual("Group", values = c("#619847", "#023bb8", "#7a608e")) +
  scale_shape_manual("Group", values=c(15,16,17)) +
  theme_bw() + 
  #Place legend at the bottom of the plot to help align x-axis of the plot and the table
  theme(legend.position="bottom")

g1

The legend can also be placed inside the plot area using the arguments legend.position=c(x, y), where x and y are the coordinates that can take values from 0 to 1.

2. Create a Table with the Mean Values and Confidence Intervals

The following r code uses the geom_text() function to create a sort of table of the mean values and confidence intervals per day.

*To get the table to align with the above plot, it is important to use the same axis specifications as the plot.

t1 <- ggplot(data=statsBG) +
  geom_text(aes(y=groupid, x=timedays, label=paste0(round(n_size, digits=0)), hjust=1, vjust=0.5)) +
  ggtitle("Number of Patients") +
  #Thesame x-axis specifications as the above plot to ensure alignment
  scale_x_continuous(breaks=seq(1,10,1), limits = c(0.5,10.5)) +
  #Reverse y-axis to show Group A to C instead of Group C to A
  scale_y_discrete(limits=rev) + 
  theme_classic(base_size=13) +
  #Remove axis line, ticks and axis label to get the look of a table
  theme(
    axis.line = element_blank(),
    axis.ticks  = element_blank(),
    axis.title.y  = element_blank(),
    axis.title.x  = element_blank(),
    axis.text.x = element_text(color="white"),
    plot.title = element_text(size=11, hjust =-0.06)
  )

t1

3. Combine Plot and Table

To combine the plot and table above, we need to install and load the gridExtra package.

Combining the Plot and Table Using grid.arrange(…, ncol=1)

Combining the Plot and Table Using a Layout Matrix

The layout matrix is used for more complex layouts. But a layout matrix can also be used in our simple case. If we want the height of the plot to be three times that of the table below it, we can use the following layout matrix.

Alternatively, we can use the ggarrange() function from the ggpubr package to achieve the same results as above. The ggpubr package also uses the grid.arrange() function:

install.packages("ggpubr")
library(ggpubr)
ggarrange(g1, t1, ncol = 1, heights = c(4, 1))

You may also want to read the following article that illustrates how to create forest plots, combining the plot and table side by side.