The option W in Fit()?

"W" [Set]( all weights to 1; ignore error bars


Sorry for a naive query, but can someone please help explain option W while using the Fit() method? I understand it sets weights to 1, but I am not sure as to what do the ‘weights’ refer here.

Thanks a lot

Keep reading that section, scrolling down a bit you’ll read about fitting TGraphErrors. More recent documentation has a bit more explanations: