title: Remove Columns from a table that are 90% one value
body: <p>Example Data:</p>
  <pre><code>A&lt;- c(1,2,3,4,1,2,3,4,1,2)
  B&lt;- c(A,B,C,D,E,F,G,H,I,J)
  C&lt;- c(1,1,1,1,1,1,1,1,1,0)
  D&lt;- c(TRUE,TRUE,TRUE,TRUE,TRUE,TRUE,TRUE,TRUE,TRUE,FALSE)
  df1&lt;-data.frame(A,B,C,D)
  
  df1 %&gt;%
    select_if(
      ###column is &lt;90% one value
    )
  </code></pre>
  <p>So I have a table that has a few columns that are predominantly one value--like C and D in the above example. I need to get rid of any columns that are 90% or more one unique value. How can I get rid of the columns that fit this criteria?</p>