How to save ggplot2 plot to pdf with high resolution?

To save a ggplot2 plot to a pdf file with high resolution, you can use the ggsave() function.

Here is an example code snippet:

library(ggplot2)

# create a sample plot
my_plot <- ggplot(mtcars, aes(x=wt, y=mpg)) + 
             geom_point() + 
             labs(title="My Plot")

# save the plot to a pdf file with high resolution
ggsave("my_plot.pdf", plot=my_plot, width=10, height=8, dpi=300)

In this example, we first create a sample ggplot2 plot called my_plot. Then, we use the ggsave() function to save the plot to a pdf file called “my_plot.pdf”. We also specify the width, height, and dpi arguments to adjust the size and resolution of the saved plot.

How to combine two plots with adding letters a and b to the top right of the subplots?

You can use the patchwork package. Here is an example code:

library(ggplot2)
library(patchwork)

# Create two sample plots
p1 <- ggplot(mtcars, aes(x=wt, y=mpg)) + geom_point() + ggtitle("Plot A")
p2 <- ggplot(mtcars, aes(x=wt, y=disp)) + geom_point() + ggtitle("Plot B")

# Combine the plots using patchwork
(p1 + plot_spacer() + p2) + 
  plot_layout(ncol=2, widths=c(1,1), heights=c(1,1), guides = 'collect') + 
  plot_annotation(tag_levels = 'A', tag_suffix = ")")

In this example, p1 and p2 are the two ggplot2 plots you want to combine. plot_spacer() adds a blank space between the two plots. plot_layout() specifies the layout of the combined plots. plot_annotation() adds the letters “A” and “B” to the top right of each subplot, and the tag_suffix argument specifies the closing parenthesis for the letters.