Filter1d -E

Can anyone give me more information about the -E option in filter1d ?
In particular how it derive information at the data end ?

“-E Include Ends of time series in output. Default loses half the filter-width of data at each end.”

thanks a lot

The -E means we run the convolution centred on all those nodes in the first and last section corresponding to the half filter width. Thus, it is unbalanced since there are no data before the first one and no data after the last point. So in a sense the filtering gets narrower for the output. Use with caution since nothing can replace knowing the actual values. so we only use -E when it is convenient to have the output range match the input and we are not that concerned about the filtered output being a bit shabby at beginning and end.