One of the three measures of fit reported by ALSCAL, RSQ is the simplest to understand, but is not optimized by ALSCAL.
RSQ is the squared correlation between the disparities and the distances. The disparities are the data, after being optimally transformed to maximize the S-STRESS measure. The distances are generated by the model. Thus, RSQ measures the fit of the model to the transformed data. The measure can be interpreted as indicating the proportion of variance in the transformed data which is accounted for by the model's distances. RSQ is a goodness-of-fit measure, with 1 indicating perfect fit and 0 indicating complete lack of fit.
