asfreq() issue with 'method' parameter
Hi all,

I've noticed the following behaviour in .asfreq method when dealing with frames/series containing original NaN values. When calling for instance asfreq('W-FRI',method='ffill') only NaN generated by DateOffset are forward filled, while the already present NaN values are not treated. I'm trying to figure out whether this was an intentional feature or a bug. In the former case however I would say that the documentation is a bit misleading

http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.asfreq.html

Indeed, the description of parameter 'method' is exactly equivalent to that present in fillna, 

http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.fillna.html

so it comes natural to expect all invalid observations be filled.

Thanks for your help,
Umberto
