RWLeastSqQRPvtCalc
Class RWLeastSqQRPvtCalc uses essentially the same QR method described in RWLeastSqQRCalc , except that the QR decomposition is formed using pivoting.
 
Pros:
Calculation succeeds for regression matrices of less than full rank. However, calculations fail if the regression matrix contains a column of all 0s.
Cons:
Slower than the straight QR technique described in RWLeastSqQRCalc.