[cctbxbb] Correlation coefficient for symmetry-related reflections

Hi everyone, I'm analyzing a diffraction dataset with very weak intensities and I'm getting extremely high R-linear values. Though this may simply be due to poor data, I'd like to calculate the correlation coefficient between sets of symmetry-related reflections to make sure the low intensity values aren't artificially inflating the observed R-linears. Is there a way to do this in Phenix or cctbx? Thanks! -Andrew