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This page describes the legacy workflow. New features might not be compatible with the legacy workflow. For the corresponding step in the recommended workflow, see evaluateGradient.

Description

[ux,uy] = pdegrad(p,t,u) returns the gradient of u evaluated at the center of each triangle.

Row i from 1 to N of ux contains

$\frac{\partial {u}_{i}}{\partial x}$

Row i from 1 to N of uy contains

$\frac{\partial {u}_{i}}{\partial y}$

There is one column for each triangle in t in both ux and uy.

Although pdegrad returns the value of the gradient at the center of a triangle, the gradient is actually the same everywhere in the triangle interior. This is because pdegrad uses only linear basis functions. The boundaries of triangles are a special case: here the derivatives might be discontinuous.

The geometry of the PDE problem is given by the mesh data p and t. For details on the mesh data representation, see initmesh.

The optional argument sdl restricts the computation to the subdomains in the list sdl.