vlt.math.rectify

  vlt.math.rectify - Rectify around 0

   R = vlt.math.rectify(X)

   Returns X except where X is less than 0,
   in which case 0 is returned.

   One can also use the form:

   R = vlt.math.rectify(X, RECTVALUE)

   where points below 0 are given the value RECTVALUE.