public void transpose() {
    float temp;
    temp = m01; m01 = m10; m10 = temp;
    temp = m02; m02 = m20; m20 = temp;
    temp = m03; m03 = m30; m30 = temp;
    temp = m12; m12 = m21; m21 = temp;
    temp = m13; m13 = m31; m31 = temp;
    temp = m23; m23 = m32; m32 = temp;
  }