iteratively apply ggplot function within a map function - r

Question

I would like to generate a series of histograms for all variables in a dataset, but I am clearly not preparing the data correctly for use in the map function.
library(tidyverse)
mtcars %>%
select(wt, disp, hp) %>%
map(., function(x)
ggplot(aes(x = x)) + geom_histogram()
)
I can accomplish this task with a for loop (h/t but am trying to do the same thing within the tidyverse.
foo <- function(df) {
nm <- names(df)
for (i in seq_along(nm)) {
print(
ggplot(df, aes_string(x = nm[i])) +
geom_histogram())
}
}
mtcars %>%
select(wt, disp, hp) %>%
foo(.)
Any help is greatly appreciated.

Answer 1

Something like this would also work:
library(purrr)
library(dplyr)
mtcars %>%
select(wt, disp, hp) %>%
names() %>%
map(~ggplot(mtcars, aes_string(x = .)) + geom_histogram())
or:
mtcars %>%
select(wt, disp, hp) %>%
{map2(list(.), names(.), ~ ggplot(.x, aes_string(x = .y)) + geom_histogram())}

Answer 2

To use purrr::map, you could melt your data frame, and then split it based on the variable name into a list of data frames
library(reshape2)
library(dplyr)
library(ggplot2)
library(purrr)
melt(mtcars) %>%
split(.$variable) %>%
map(., ~ggplot(.x, aes(x=value)) +
geom_histogram())
You can also use ggplot2::facet_wrap to plot them all at once
library(reshape2)
library(dplyr)
library(ggplot2)
melt(mtcars) %>%
ggplot(., aes(x=value, label=variable)) +
geom_histogram() +
facet_wrap(~variable, nrow=ncol(mtcars))