title: Acces Cell Data from Paraview Programmable Filter
body: <p>I need to create a programmable filter using Paraview.
  The idea is to create a vector called Speed equal to the speed in the non-rotating part equal to the speed+rotational speed in the rotational one.</p>
  
  <p>The problem is that I can't accept the value of the speed in each single cell.</p>
  
  <pre><code>input0 = inputs[0]
  radius=3
  Speed1=input0.PointData["U"]
  K=vtk.vtkDoubleArray()
  X=input0.PointData["X"]
  Y=input0.PointData["Y"]
  Z=input0.PointData["Z"]
  
  pdi = self.GetInput()
  numPts = pdi.GetNumberOfPoints()
  
  for i in range(0, numPts):
      if X.getvalue(i)^2+Y.getvalue(i)^2&lt;radius:
      temp=U.getvalue(i)
      else:
      temp=U.getvalue(i)+rot
  Speed.InsertNextValue(1)
  output.PointData.append(Speed, "Speed")
  </code></pre>
  
  <p>The problem is that <code>X.getvalue(i)</code> is not working.</p>