convolve_fft defaults and documentation

I’ve just been trying to run some code that I haven’t used for a year or two, when I had an older version of astropy installed (I’m now running 2.0.10). It was giving very strange results and I eventually managed to track this done to convolve_fft. I found that if I change my convolve_fft(image,psf) to convolve_fft(image,psf,nan_treatment='fill',normalize_kernel=False) I could then reproduce the results I was getting previously. I take it the defaults were changed at some point, presumably related to #926. Can I suggest that it would make debugging old code much easier if changes that break backwards compatibility, such as this, are noted in the documentation? I’m thinking of something along the lines of http://docs.astropy.org/en/v2.0.x/io/fits/api/files.html#writeto where it clearly states ‘Changed in version 1.3: overwrite replaces the deprecated clobber argument.’

The examples also need to be completely rewritten as they were clearly written using the old defaults. For instance, the second one convolve_fft([1, np.nan, 3], [1, 1, 1]) now gives the result array([0.5, 2. , 1.5]).

[astromark]

As the person who originally reported this issue, I should probably chime in here. It’s great that the doctests were fixed. Still, I wonder if there could still be some improvements to the documentation. For instance, it doesn’t really make sense for there to be examples with keywords that are the defaults anyway since these all show the same result e.g.:

convolve_fft([1, np.nan, 3], [1, 1, 1])
convolve_fft([1, np.nan, 3], [1, 1, 1], nan_treatment='interpolate')
convolve_fft([1, np.nan, 3], [1, 1, 1], nan_treatment='interpolate', normalize_kernel=True)

all give the same result and so are redundant. Examples with the previous defaults of nan_treatment=‘fill’ and normalize_kernel=False would be more useful.

[aaryapatil]

Ah, I’ll find another one then. There don’t seem to be many first contributor issues…