R 保存图片的几种方法

print(): print a ggplot to a file
To print directly a ggplot to a file, the function print() is used:

# Print the plot to a pdf file

pdf("myplot.pdf")
myplot <- ggplot(mtcars, aes(wt, mpg)) + geom_point()
print(myplot)
dev.off()

For printing to a png file, use:

png("myplot.png")

myplot <- ggplot(mtcars, aes(wt, mpg)) + geom_point()
print(myplot)
dev.off()

ggsave: save the last ggplot
ggsave is a convenient function for saving the last plot that you displayed. It also guesses the type of graphics device from the extension. This means the only argument you need to supply is the filename.

It’s also possible to make a ggplot and to save it from the screen using the function ggsave():

# 1. Create a plot
# The plot is displayed on the screen

ggplot(mtcars, aes(wt, mpg)) + geom_point()

# 2. Save the plot to a pdf

ggsave("myplot.pdf")

For saving to a png file, use:

ggsave("myplot.png")

参考：
ggsave : Save a ggplot - R software and data visualization