r - How do pipes work with purrr map() function and the "." (dot) symbol -

when using both pipes , map() function purrr, confused how data , variables passed along. instance, code works expect:

library(tidyverse)  cars %>%    select_if(is.numeric) %>%    map(~hist(.)) 

yet, when try similar using ggplot, behaves in strange way.

cars %>%    select_if(is.numeric) %>%    map(~ggplot(cars, aes(.)) + geom_histogram()) 

i'm guessing because "." in case passing vector aes(), expecting column name. either way, wish pass each numeric column ggplot function using pipes , map(). in advance!

cars %>%    select_if(is.numeric) %>%    map2(., names(.),         ~{ggplot(data_frame(.x), aes(.x)) +             geom_histogram() +             labs(x = .y)                    }) 

there's few steps.

• use map2 instead of map. first argument dataframe you're passing it, , second argument vector of names of dataframe, knows map over.
• you need explicitly enframe data, since ggplot works on dataframes , coercible objects.
• this gives access .y pronoun name plots.