title: R.NET invoke function does not work
body: <p>I have all the necessary requirements when using the R.NET from <a href="http://rdotnet.codeplex.com/" rel="nofollow">http://rdotnet.codeplex.com/</a></p>
  
  <p>My code works just fine on R Studio, however no luck on GUI. Can anybody let me know what I am doing wrong please?</p>
  
  <pre><code>REngine.SetEnvironmentVariables(@"C:\Program Files\R\R-3.1.1\bin\i386", @"C:\Program Files\R\R-3.1.1");
  
  engine = REngine.GetInstance();
  
  engine.Evaluate(@"source('C:/Users/achugh/Documents/Graphs/characterization.r')");
              engine.Evaluate(@"source('C:/Users/achugh/Documents/Graphs/sliderDataToComputer.r')");
  
  var sliderfunc = engine.Evaluate("sliderdata_yprofile").AsFunction();
  var directory = engine.CreateCharacterVector(new[] { "C:/Users/achugh/Documents/Graphs/data" });
  var oldset = sliderfunc.Invoke(new SymbolicExpression[] { directory }).AsDataFrame();
  </code></pre>
  
  <p>But for some reason the 'oldset' always evaluates to NULL. I already tried testing this via R-Studio</p>
  
  <p>please advice?</p>