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

Unless I'm missing something, generating plots by a subsetting variable is very simple. You can use split(...) to split the original data into a list of data frames by NetworkTrackingPixelId, and then pass those to ggplot using lapply(...). Most of the code below is just to crate a sample dataset.

# create sample data
set.seed(1)
names <- c("Rubicon","Google","OpenX","AppNexus","Pubmatic")
dates <- as.Date("2014-02-16")+1:10
df <- data.frame(NetworkTrackingPixelId=rep(1:5,each=10),
                 Name=sample(names,50,replace=T),
                 Date=dates,
                 Impressions=sample(1000:10000,50))
# end create sample data

pdf("plots.pdf")
lapply(split(df,df$NetworkTrackingPixelId),
       function(gg) ggplot(gg,aes(x = Date, y = Impressions)) + 
          geom_point() + geom_line()+
          ggtitle(paste("NetworkTrackingPixelId:",gg$NetworkTrackingPixelId)))
dev.off()

This generates a pdf containing 5 plots, one for each NetworkTrackingPixelId.