The Robust parameter is indeed taken into account in the calculation of the Goodness-of-fit statistics when using the fit function. This can be seen by comparing the gof outputs from a robust fit to those from a non-robust fit:
load census
[f,gof1] = fit(cdate,pop,'poly3','Normalize','on');
[f,gof2] = fit(cdate,pop,'poly3','Normalize','on','Robust','Bisquare');
disp(gof1)
disp(gof2)
This can also been seen by stepping through the code of the fit function, which can be accessed by:
edit fit
At line 413, when the Robust parameter is set, the iRobustLinearFit function is called instead of iLinearFit. The residuals are adjusted through some calculations based on the robust weights. These weighted residuals subsequently influence the calculation of the Goodness-of-fit metrics in the iGoodnessStructure function.
Hope this clarifies the issue!
