code: public static ZMatrixRMaj rectangle(int numRow , int numCol , Random rand ) {
          return rectangle(numRow,numCol,-1,1,rand);
      }
docs: <p>
  Returns a matrix where all the elements are selected independently from
  a uniform distribution between -1 and 1 inclusive.
  </p>
  
  @param numRow Number of rows in the new matrix.
  @param numCol Number of columns in the new matrix.
  @param rand Random number generator used to fill the matrix.
  @return The randomly generated matrix.