[Numpy-discussion] Faster NaN functions

Hi, I just send a pull request for some faster NaN functions, https://github.com/rigtorp/numpy. I implemented the following generalized ufuncs: nansum(), nancumsum(), nanmean(), nanstd() and for fun mean() and std(). It turns out that the generalized ufunc mean() and std() is faster than the current numpy functions. I'm also going to add nanprod(), nancumprod(), nanmax(), nanmin(), nanargmax(), nanargmin(). The current implementation is not optimized in any way and there are probably some speedups possible. I hope we can get this into numpy 2.0, me and people around me seems to have a need for these functions. Erik