If you download the files and run
dpkg-source -x matplotlib_0.98.1-1.dsc cd matplotlib-0.98.1/ patch -Np1 < ../matplotlib_0.98.1-1ubuntu1.debdiff
then you have to remove the hidden directory .pc from source folder. patch only removes the content of the files instead of deleting the files in .pc.
If you download the files and run
dpkg-source -x matplotlib_ 0.98.1- 1.dsc 0.98.1- 1ubuntu1. debdiff
cd matplotlib-0.98.1/
patch -Np1 < ../matplotlib_
then you have to remove the hidden directory .pc from source folder. patch only removes the content of the files instead of deleting the files in .pc.