arrange multiple graphs using a for loop in ggplot2

Question

I want to produce a pdf which shows multiple graphs, one for each NetworkTrackingPixelId. I have a data frame similar to this:

> head(data)
  Net         


        

Answer 1

Since I don't have your dataset, I will use the mtcars dataset to illustrate how to do this using dplyr and data.table. Both packages are the finest examples of the split-apply-combine paradigm in rstats. Let me explain:

Step 1 Split data by gear

• dplyr uses the function group_by
• data.table uses argument by

Step 2: Apply a function

• dplyr uses do to which you can pass a function that uses the pieces x.
• data.table interprets the variables to the function in context of each piece.

Step 3: Combine

There is no combine step here, since we are saving the charts created to file.

library(dplyr)
mtcars %.%
  group_by(gear) %.%
  do(function(x){ggsave(
    filename = sprintf("gear_%s.pdf", unique(x$gear)), qplot(wt, mpg, data = x)
  )})

library(data.table)
mtcars_dt = data.table(mtcars)
mtcars_dt[,ggsave(
  filename = sprintf("gear_%s.pdf", unique(gear)), qplot(wt, mpg)),
  by = gear
]

UPDATE: To save all files into one pdf, here is a quick solution.

plots = mtcars %.%
  group_by(gear) %.%
  do(function(x) {
    qplot(wt, mpg, data = x)
  })

pdf('all.pdf')
invisible(lapply(plots, print))
dev.off()