R assigning ggplot objects to list in loop

Question

I\'m using a for loop to assign ggplots to a list, which is then passed to plot_grid() (package cowplot). plot_grid

Answer 1

I believe the problem here is that the non-standard evaluation of the aes method delays evaluating i until the plot is actually plotted. By the time of plotting, i is the last value (in the toy example "B") and thus the y aesthetic mapping for all plots refers to that last value. Meanwhile, the labs call uses standard evaluation and so the labels correctly refer to each iteration of i in the loop.

This can be fixed by simply using the standard evaluation version of the mapping function, aes_q:

require(cowplot)

dfrm <- data.frame(A=1:10, B=10:1)

v <- c("A","B")
dfmsize <- nrow(dfrm)
myplots <- vector("list",2)

count = 1
for(i in v){
    myplots[[count]] <- ggplot(dfrm, aes_q(x=1:dfmsize, y=dfrm[,i])) + geom_point() + labs(y=i)
    count = count +1
}
plot_grid(plotlist=myplots)