Hi Edward, I've been using the 1.3.6. version of Relax today. It is excellent at recognising the Analysis2.1 Sparky formatted files now, thank you Edward, but I thought I might try using my old lists and changing the int_method function in Relax curve fit from 'height' to 'volume' (as they were volume all along!) to see what answers I get - will it get me accurated results - in the manual, it says that error is calculated in the same way as long as you have replicated spectra for either height or volume - is this true? Apart from these queries I think I've come across a problem... In the test suite, using 'height' as the in_method function, there are no problems. But when you change to 'point_sum' or 'point sum' as it says in the manual (tried both), the program says the options are height, volume or other. I've tried putting in 'volume', but I get the following error. ----------------------------- relax> spectrum.replicated(spectrum_ids=['T2_ncyc1_ave', 'T2_ncyc1b_ave']) relax> spectrum.replicated(spectrum_ids=['T2_ncyc4_ave', 'T2_ncyc4b_ave']) relax> spectrum.replicated(spectrum_ids=['T2_ncyc9_ave', 'T2_ncyc9b_ave']) relax> spectrum.replicated(spectrum_ids=['T2_ncyc11_ave', 'T2_ncyc11b_ave']) relax> spectrum.error_analysis() Intensity measure: Peak volumes. Replicated spectra: Yes. RelaxError: This function has not yet been implemented. ----------------------------- Is this a problem from changing between 'point sum' and 'volume' nomenclature at some point? Madeleine Strickland MCJC Group N317, School of Chemistry, Bristol University