title: How to unite() and show asterix with values for significance within dataframe
body: <p>I have this df with a lot of coefficients in one column and asterixs in the next column. I am trying to unite() the two columns but i get an error. I made an example:</p>
  
  <pre><code>library(dplyr)
  # creating df
  df &lt;- tibble(city = c("amsterdam", "amsterdam", "amsterdam", "rotterdam", "rotterdam", "rotterdam"),
                  terms = c("intercept", "food", "service", "intercept", "food", "service"),
                  coefficient = c(23, .54, -.02, 18, .86, .67),
                  p.value = c("***", "*", " ", "***", "***", "**"))
  
  # Here i try to unite the two columns
  df %&gt;% 
    mutate(coefficient = unite(coefficient, p.value, sep = ""))
  </code></pre>
  
  <p>When i run this i get the following error message:</p>
  
  <pre><code>Error in mutate_impl(.data, dots) : 
    Evaluation error: no applicable method 
  for 'unite_' applied to an object of class 
  "c('double', 'numeric')".
  </code></pre>
  
  <p>Can anyone tell me how to solve this? If possible also it would be nice if the final column is aligned in such a way that the minus sign starts earlier than the numbers in the final column)</p>