CODEWITHSUNDEEP
rggplot2lapply
KerrBer
KerrBer

Reputation: 129

Separate plot titles within lapply

I have a number of objects which I would like to plot together on one page, with a separate title for each. At the moment, I have a vector of plot titles which I feed into ggtitle within lapply, but it adds only the first entry of this vector to each plot.

A quick and ugly minimal example is below:

library(ggplot2)
library(gridExtra)

#My 'data'
A.a <- rnorm(10)
A.b <- rnorm(30)
lmnames <- ls(pattern = "A.*")

titlenames <- c("Plot A", "Plot B")

plotlist <- list()
#I have a more complex ggplot function in reality, but I'm using qplot here as a placeholder.
plotlist <- lapply(lmnames, FUN=function(x,y){qplot(get(x)) + ggtitle(y)}, y=titlenames)

grid.arrange(grobs = plotlist)

It looks like this: Incorrect titles using ggtitle in lapply

You can see, both plots are labelled "Plot A". I'd like to have each plot labelled accordingly. Can anyone help me see what I'm missing here? Thanks in advance.

Upvotes: 3

Views: 1492

Answers (3)

baptiste
baptiste

Reputation: 77096

Looping over multiple variables is often cleaner with mapply,

library(ggplot2)
library(gridExtra)

dl <- list("Plot A" = rnorm(10), "Plot B" = rnorm(10))
plot_fun <- function(x, y) qplot(x) + ggtitle(y)
grid.arrange(grobs = Map(plot_fun, x = dl, y = names(dl)))

enter image description here

Upvotes: 2

J_F
J_F

Reputation: 10352

Your problem is, that in all your plots, your title is "Plot A" "Plot B", see plotlist[[1]]$labels$title.

A working code is the following:

plotlist <- lapply(1:length(lmnames), function(x){
  qplot(get(lmnames[x])) + ggtitle(titlenames[x])
})

I'm sure there are more elegant solutions. But this one will work.

Regards, J_F

Upvotes: 4

zyurnaidi
zyurnaidi

Reputation: 2263

This works fine:

plotlist <- lapply(1:2, FUN=function(i){qplot(get(lmnames[i])) + ggtitle(titlenames[i])})

Or this:

plotlist <- apply(data.frame(lmnames, titlenames), 1, FUN=function(x){qplot(get(x[1])) + ggtitle(x[2])})

enter image description here

The issue is that in both iteration, only the first value of y=titlenames is read in

Upvotes: 0

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