COMSOL Forums: Finding the gradient of a quantity (surface charge) on a surface...help! http://www.comsol.no/community/forums/general/thread/3746/ Most recent forum messages Thu, 11 Mar 2010 17:41:24 +0000 COMSOL Forums: Finding the gradient of a quantity (surface charge) on a surface...help! http://www.comsol.no/shared/images/logos/comsol_logo.gif http://www.comsol.no/community/forums/general/thread/3746/ Finding the gradient of a quantity (surface charge) on a surface...help! http://www.comsol.no/community/forums/general/thread/3746/#p9722 Hello,<br /> I'm a beginner and can't find help on this in the manual:<br /> I'm doing an electrostatics model, and I get out the charge density on a surface, but I want to know the gradient of the charge density, particularly in one direction (z). I've tried diff(nD_es,z) and diff(nD_es,t2z) and both just give me 0. Does anyone know how to take a derivative on a surface? Thank you!<br /> Anna Thu, 11 Mar 2010 17:41:24 +0000 3746.1268329284.9722