comment on numpy/pandas interaction when calling amin() on a pandas DataFrame
I noticed the following in tracking down a problem a user of ours encountered. Not sure this is a bug per se and with the caveat that I'm not a Python expert, but I thought I would mention it.

This is occurring with pandas 0.12.0 but given the nature of the issue is probably present in more recent versions.

If a user calls numpy's amin() [or amax()] on a pandas DataFrame, then within amin() the following lines of code will often be called

```
amin = a.min
amin(axis = axis, out = out)
```

The problem is that if the first argument to amin() is a pandas dataframe then the min method for 'a' inside amin() is the pandas dataframe min method, which does not take 'out' as an argument. This is for numpy 1.8.0.

The above issue was disguised somewhat in earlier numpy versions (e.g. 1.6.1) because 'out' was not a named argument, instead the line above was 
amin(axis,out)
so in many cases the call to amin() would return a result.

Perhaps users shouldn't be calling amin() or amax() on pandas dataframes but nothing prevents them from doing so, resulting in what is a fairly subtle bug in their code and (at least in later numpy versions) an error message that requires a bit of investigation of the code in amin() to understand.

-Chris

---

Chris Paciorek 

Statistical Computing Consultant
Statistical Computing Facility and Econometrics Laboratory

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