$ sudo apt-get remove libplplot12 

Uninstall libplplot12 including dependent package

If you would like to remove libplplot12 and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove libplplot12 

Use Purging libplplot12

If you use with purge options to libplplot12 package all the configuration and dependent packages will be removed.

$ sudo apt-get purge libplplot12 

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 libplplot12 

See Also,