$ sudo apt-get remove fftw-docs 

Uninstall fftw-docs including dependent package

If you would like to remove fftw-docs and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove fftw-docs 

Use Purging fftw-docs

If you use with purge options to fftw-docs package all the configuration and dependent packages will be removed.

$ sudo apt-get purge fftw-docs 

If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.

$ sudo apt-get purge --auto-remove fftw-docs 

See Also,