R为单个pdf生成多个图

Question

I have a list of about 100 different groups;

categories <- c('cat1','cat2','cat3',....)

I would like to write a loop that goes and grabs only the data for 1 category at a time, and generate a plot (x,y); for example...

for (i in 1:length(categories){
category_data <- data[which(data$category==categories[i]),]
plot(category_data$y,category_data$x)}
### however, I would like to save EACH plot to a single PDF that I can scroll through to quickly visualize everything at once

How can I generate a single PDF with 100 different plots?

Answer 1

You can generate a multiple page pdf by using the pdf function (or png, jpeg, etc), generating all of the files that you want to and then closing the file with dev.off

pdf(file = "output.pdf")

for (i in 1:length(categories){
   category_data <- data[which(data$category==categories[i]),]
   plot(category_data$y,category_data$x)}

dev.off()

Answer 2

I used R for much of the graphing in my college statistics and calculus classes. The best way I found to incorporating multiple plots into a single PDF was to apply the principle of Separation of Concerns .

R was great at generating the plots (I favored the png format), but LaTeX rocked for generating PDFs. My simplified workflow looked something like this:

1. Generate the plots in a known folder, with sequentially generated names ( graph_01.png , etc).
2. Open a template file I kept around to avoid having to recreate the boilerplate code.
3. Use a shell script to generate markup needed to insert the image.
4. Do any manual cleanup, add captions, etc.
5. Generate the pdf using pdflatex

It was very easy, and almost completely automated.

Answer 3

Based on the OP wanting 4 plots per PDF page, I would recommend:

pdf('plots.pdf')
par(mfrow=c(2,2))
for (i in 1:length(categories){
    category_data <- data[which(data$category==categories[i]),]
    plot(category_data$y,category_data$x)}
dev.off()

If the OP decides to plot a different number of graphs per page, the mfrow parameter can be changed. Currently it is set for 2 rows x 2 columns = 4 plots per page.