Rotational and population diagrams of deuterated methanol isotopologues (CH₂ DOH, CH₃ OD, and CHD₂OH) derived towards NGC 1333-IRAS 2A for source sizes derived from the PD analysis of the methanol population distribution (0′′.20; see Taquet et al. 2015). Red, green, and blue symbols represent transitions at 145, 165, and 225 GHz, respectively. The CH₃ OD and CHD₂OH levels have been artificially shifted by −1.5 and −4 for clarity. Observational data are depicted by diamonds. Crosses show the best fit of the PD to the data. Blue and green symbols represent transitions at 2 and 1.3 mm, respectively. Error bars are derived assuming a calibration uncertainty of 20% in addition to the statistical error. Black straight lines represent the best fit of the rotational diagram analysis to the data, assuming optically thin emission.