how to print a list-column of ggplots to pdf?

Question

Consider this funny example

mydata <- data_frame(group = c('a', 'a', 'a', 'b', 'b', 'b'),
           x = c(1,2,3,5,6,7),
           y = c(3,5,6,4,3,2))

> mydata
# A tibble: 6 x 3
  group     x     y
  <chr> <dbl> <dbl>
1 a         1     3
2 a         2     5
3 a         3     6
4 b         5     4
5 b         6     3
6 b         7     2

Here I can nest() by group, and store a group-based ggplot into a list-column . Crazy stuff.

> mydata %>% group_by(group) %>% 
+   nest() %>% 
+   mutate(myplot = map(data, ~ggplot(data = .x, aes(x = x, y = x)) + geom_point()))
# A tibble: 2 x 3
  group data             myplot  
  <chr> <list>           <list>  
1 a     <tibble [3 x 2]> <S3: gg>
2 b     <tibble [3 x 2]> <S3: gg>

However, I would like to use map to print each of these charts into a single pdf . That is, one pdf page per group.

Here I am at a loss. How can I do that? Thanks!

Answer 1

Just open the pdf device and print them :)

library(tidyverse)
mydata <- data_frame(group = c('a', 'a', 'a', 'b', 'b', 'b'),
                     x = c(1,2,3,5,6,7),
                     y = c(3,5,6,4,3,2))

mydata2 <- mydata %>% group_by(group) %>% 
  nest() %>% 
  mutate(myplot = map(data, ~ggplot(data = .x, aes(x = x, y = x)) + geom_point()))

pdf()
print(mydata2$myplot)
dev.off()

As @aosmith comments you can skip the print call if you're using R interactively, but be careful that if you wrap it later into a function it won't work anymore, so I'd recommend to keep it explicit.

If you want to chain it :

pdf()
mydata %>% group_by(group) %>% 
  nest() %>% 
  mutate(myplot = map(data, ~ggplot(data = .x, aes(x = x, y = x)) + geom_point())) %>%
  pull(myplot) %>%
  print
dev.off()

The first argument of pdf is the path of your printed file and by default it's "Rplots.pdf" , so it will be in your working folder. See ?pdf for more.