title: Converting column type from String to Int in a DataFrame in Julia
body: <p>I want to change column datatype in Julia from string to int but no luck so far. Neither <code>convert()</code> nor <code>parse()</code> works. Is there any way to do that?</p>
  
  <p>I have tried these but none works</p>
  
  <p><code>df[:serial] = int.(collect(df[:strSerial]))
   df[:serial] = map(x-&gt;parse(Int,x),df[:strSerial])
   df[:serial] = Int64(df[:strSerial])</code></p>