$ sudo apt-get remove dia-libs 

Uninstall dia-libs including dependent package

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

$ sudo apt-get remove --auto-remove dia-libs 

Use Purging dia-libs

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

$ sudo apt-get purge dia-libs 

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 dia-libs 

See Also,