docs: public static ZMatrixRMaj[] columnsToVector(ZMatrixRMaj A, ZMatrixRMaj[] v)
      {
          ZMatrixRMaj[]ret;
          if( v == null || v.length < A.numCols ) {
              ret = new ZMatrixRMaj[ A.numCols ];
          } else {
              ret = v;
          }
  
          for( int i = 0; i < ret.length; i++ ) {
              if( ret[i] == null ) {
                  ret[i] = new ZMatrixRMaj(A.numRows,1);
              } else {
                  ret[i].reshape(A.numRows,1);
              }
  
              ZMatrixRMaj u = ret[i];
  
              int indexU = 0;
              for( int j = 0; j < A.numRows; j++ ) {
                  int indexA = A.getIndex(j,i);
                  u.data[indexU++] = A.data[indexA++];
                  u.data[indexU++] = A.data[indexA];
              }
          }
  
          return ret;
      }