title: Get Column names using pipes r
body: <p>I am trying to get column names of NA columns using named pipes in R:-</p>
  
  <pre><code>df &lt;- structure(data.frame(id = c(1, 2, NA, NA, NA, NA), 
                   cat = c("SS","SS", "SS", "SV", "SV", "SV"),
                   val = c(220L, 222L, 223L, NA,NA, 2206L)),
                  .Names = c("id", "cat", "val"), class = "data.frame",
                    row.names = c(NA,-6L)) 
  
  sapply(df, function(x) ((sum(is.na(x))))*.01)%&gt;%
    stack %&gt;% rev %&gt;% filter(values &gt; 0) %&gt;% setNames(nm=c("variable", "missing"))%&gt;%
  paste0(colnames -&gt;NulCols)
  </code></pre>
  
  <p>But the code gives out error. 
  Error in paste0(., NulCols &lt;- colnames) : 
    cannot coerce type 'closure' to vector of type 'character'</p>
  
  <p>Want to create a list of NA Columns using named pipes only.</p>