Install.rst is missing references to optional packages

[jlec]

Following references are missing

• rpy2
• psycopg (at least testing needs it)
• pymysql (at least testing needs it)
• matplotlib

perhaps there are more.

[jorisvandenbossche]

Thanks for the report!

matplotlib is mentioned (http://pandas.pydata.org/pandas-docs/stable/install.html#optional-dependencies), rpy2 is for a deprecated module, so I don't think it is worth to add it.
For psycopg2 and pymysql, I think we can add these as 'examples' of database drivers that you need together with sqlalchemy (because there are many more possibilities to install).

[jlec]

I overlooked matplotlib.

Regarding rpy I read the docs as if the pandas.rpymodule is deprecated but you can/should use rpy2 to interface with R.

[jorisvandenbossche]

On rpy2, you are correct that it is pandas.rpy that is deprecated, but for pandas itself, rpy2 is only needed for that module. You can of course use more in general rpy2 to interface with R, but I don't think this should be included in the 'install' part for pandas (we cannot add every library that can be used together with pandas, therefore there is eg the ecosystem page in the docs).