The option W in Fit()?

Newbie
1 
"W" [Set](https://root.cern.ch/root/html528/TGraph.html#TGraph:Set) all weights to 1; ignore error bars

Hi,

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

2

Keep reading that section, scrolling down a bit you’ll read about fitting TGraphErrors. More recent documentation has a bit more explanations:
https://root.cern/doc/master/classTGraph.html#aa978c8ee0162e661eae795f6f3a35589