code: public static double normP2( DMatrixRMaj A ) {
          if( MatrixFeatures_DDRM.isVector(A)) {
              return normF(A);
          } else {
              return inducedP2(A);
          }
      }
docs: Computes the p=2 norm.  If A is a matrix then the induced norm is computed.
  
  @param A Matrix or vector.
  @return The norm.