title: How do I use coalesce rowise?
body: <p>I have this tibble</p>
  
  <pre><code>library(tidyverse)
  data_frame(first = c("a", NA, "b"),
             second = c(NA, "b", NA),
             third = c("a", NA, NA))
  </code></pre>
  
  <p>I would like to use <code>coalesce()</code> row-wise to grab only values that are not NA.</p>
  
  <p>The desired output would be a vector of the first non NA values that we can find inspecting the dataframe rowwise from left to righ</p>
  
  <pre><code>[1] "a" "b" "b"
  </code></pre>