# pdesurf

Surface plot of PDE node or triangle data

This page describes the legacy workflow. Use it when you work with legacy code and do not plan to convert it to use the recommended approach. Otherwise, use `pdeplot`.

## Syntax

``pdesurf(p,t,u)``
``h = pdesurf(p,t,u)``

## Description

example

````pdesurf(p,t,u)` plots a 3-D surface using PDE node or triangle data as a height for a 2-D problem. The `p` and `t` arguments specify the geometry of the PDE problem.If `u` is a column vector, `pdesurf` treats it as node data and uses continuous style and interpolated shading. If `u` is a row vector, `pdesurf` treats it as triangle data and uses discontinuous style and flat shading.```
````h = pdesurf(p,t,u)` returns handles to the drawn axes objects.```

## Examples

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Plot the solution of the equation $-\Delta u=1$ on the L-shaped membrane using the `pdesurf` function.

First, create a `[p,e,t]` mesh on the L-shaped membrane.

`[p,e,t] = initmesh('lshapeg'); `

Solve the equation using the Dirichlet boundary conditions $u=0$ on $\partial \Omega$.

`u = assempde('lshapeb',p,e,t,1,0,1);`

Plot the solution at the mesh nodes. When plotting the solution at the nodes, the function uses continuous style and interpolated shading.

`pdesurf(p,t,u)`

Interpolate the solution from the mesh nodes to the triangle midpoints.

`ut = pdeintrp(p,t,u);`

Plot the interpolated solution. When plotting the solution as a triangle data, the function uses discontinuous style and flat shading.

`pdesurf(p,t,ut)`

## Input Arguments

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Mesh points, specified as a 2-by-`Np` matrix of points, where `Np` is the number of points in the mesh. For details on the mesh data representation, see `initmesh`.

Data Types: `double`

Mesh triangles, specified as a `4`-by-`Nt` matrix of triangles, where `Nt` is the number of triangles in the mesh. For details on the mesh data representation, see `initmesh`.

Data Types: `double`

PDE solution, specified as a vector.

The `pdesurf` function treats a column vector as node data and uses continuous style and interpolated shading. The function treats a row vector as triangle data and uses discontinuous style and flat shading.

Data Types: `double`

## Output Arguments

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Handles to graphics objects, returned as a vector.