Remark: plotQuadMesh.m and plotCountorSolution.m are in the zipped file additionalFiles.zip, that can be found at Toni Susin's 'Numerical Factory',
https://numfactory.upc.edu/web/FiniteElements.html
in Section 'Extra material Files'.
Disclaimer: this stuff is provided 'as is'. Please, check it (if you find it useful), but try to write the programs on your own.
If you find any mistakes (or have any suggestions), please report them to
Many thanks,
J.R.