Creating a list of ggplots in a loop, using the in

问题:

This question already has an answer here:

Loops, dataframes and ggplot (1 answer)

Closed 5 years ago.

This loop creates a list of 3 ggplots, but because the arguments for x and xend depend on the index of the loop, dismay follows:

DF <- data.frame(column1=c(1,2,3,4,5), column2=c(4,5,6,7,8))

list_of_ggplots <- list()

for (num in seq(1:3)){ 
  p <- ggplot()
  p <- p + geom_segment(data=DF, aes(x=column1[num], xend=column2[num], y=1, yend=1))

  list_of_ggplots[[num]] <- p }
list_of_ggplots

We get 3 plots being fundamentally the same plot (since at the point in time they are called, num is 3).

What could be a better strategy to create these plots?

回答1:

You can get a list without running explicit loops by using lapply:

list_of_ggplots <- lapply(1:nrow(DF), function(i) {ggplot(DF[i,]) + aes(x=column1, xend=column2, y=1, yend=1)+geom_segment()})

回答2:

you can make the list in a more "R"-like way with lapply and then just subset DF with num vs trying to do so in the aesthetics. However, you should also use scale_x_continuous and set the limits, otherwise they'll all still "look" the same (except for the #'s on the x axis)

list_of_ggplots <- lapply(1:nrow(DF), function(num) {
  p <- ggplot()
  p <- p + geom_segment(data=DF[num,], aes(x=column1, xend=column2, y=1, yend=1))
  p + scale_x_continuous(limits=c(0, max(DF$column2))) 
})