Setting values on a copy of a slice from a DataFrame [duplicate]
This warning comes because your dataframe x is a copy of a slice. This is not easy to know why, but it has something to do with how you have come to the current state of it.
You can either create a proper dataframe out of x by doing
x = x.copy()
This will remove the warning, but it is not the proper way
You should be using the DataFrame.loc method, as the warning suggests, like this:
x.loc[:,'Mass32s'] = pandas.rolling_mean(x.Mass32, 5).shift(-2)