When using both pipes and the map() function from purrr, I am confused about how data and variables are passed along. For instance, this code works as I expect:
library(tidyverse) cars %>% select_if(is.numeric) %>% map(~hist(.))
Yet, when I try something similar using ggplot, it behaves in a strange way.
cars %>% select_if(is.numeric) %>% map(~ggplot(cars, aes(.)) + geom_histogram())
I'm guessing this is because the "." in this case is passing a vector to aes(), which is expecting a column name. Either way, I wish I could pass each numeric column to a ggplot function using pipes and map(). Thanks in advance!
cars %>% select_if(is.numeric) %>% map2(., names(.), ~{ggplot(data_frame(var = .x), aes(var)) + geom_histogram() + labs(x = .y) })
There's a few extra steps.
- Use
map2 instead of map. The first argument is the dataframe you're passing it, and the second argument is a vector of the names of that dataframe, so it knows what to map over. - You then need to explicitly enframe your data, since
ggplot only works on dataframes and coercible objects. - This also gives you access to the
.y pronoun to name the plots.
You aren't supposed to pass raw data to an aesthetic mapping. Instead you should dynamically build the data.frame. For example
cars %>% select_if(is.numeric) %>% map(~ggplot(data_frame(x=.), aes(x)) + geom_histogram())
