title: Sparkr write DF as file csv/txt
body: <p>Hi I'm working on sparkR in yarn mode.</p>
  
  <p>I need to write a sparkr df to a csv/txt file.</p>
  
  <p>I saw that there is <code>write.df</code> but it writes parquet files.</p>
  
  <p>I tried to do this things </p>
  
  <pre><code>RdataFrame&lt;-collect(SparkRDF)
  write.table(RdataFrame, ..)
  </code></pre>
  
  <p>But I got many WARN and some ERROR on contextCleaner.</p>
  
  <p>Is there any way ?</p>