title: How do pipes work with purrr map() function and the "." (dot) symbol
body: <p>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:</p>
  
  <pre><code>library(tidyverse)
  
  cars %&gt;% 
    select_if(is.numeric) %&gt;% 
    map(~hist(.))
  </code></pre>
  
  <p>Yet, when I try something similar using ggplot, it behaves in a strange way. </p>
  
  <pre><code>cars %&gt;% 
    select_if(is.numeric) %&gt;% 
    map(~ggplot(cars, aes(.)) + geom_histogram())
  </code></pre>
  
  <p>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!</p>