# How to plot temperature distribution T(X,Y) over a 2D rectangular plate in Matlab?

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Jin Au on 7 Jun 2017
Answered: Sanjay Kumar on 24 Apr 2023
Hi all,
I recently attempted to code the FEM 2D triangular element method to solve for the temperature at each node of a rectangular plate with given temperature boundary conditions. I successfully assigned the (x,y) coordinates at each node and solved the corresponding temperature at each node. By the way, the temperature is a vector. Now I would like to know how to plot a temperature distribution for the reactangular plate in Matlab. I've attempted to use surfc(x,y,T); however, Matlab returned an error that states "T needs to have more than one row or column." I appreaciate for any help provided.
Image Analyst on 7 Jun 2017
Maybe you can show a diagram. I thought you had "a rectangular plate" and to me, that means a 2-D situation where for every (x,y) location you have a temperature. I'm not sure what your "nodes" are. I'm thinking that, for example a point 2 mm over and 4 mm down from the upper left corner should have a temperature. And likewise for every location in the rectangular plate. I thought you said that every node has an (x,y) coordinate. Apparently that's not what you are envisioning, so you'll have to explain better, like with diagrams or pictures of this rectangular plate with the where these one-D Temperatures are located on that rectangular plate.
Jin Au on 7 Jun 2017
Edited: Jin Au on 7 Jun 2017
I apologize for my unclear description. Here's the diagram of the problem.

KSSV on 7 Jun 2017
You said FEM....and triangular elements....so you have used unstructured grid. You should be having (x,y) points in the form of nX2 array and nodal connectivity data (say tri)in the form of nX3 array. So you have evaluated temperature T at each node; this is nX1 array, where n is the number of nodes. You can plot this using: trisurf
trisurf(tri,x,y,T)
doc triplot, trimesh , trisurf .
Jin Au on 7 Jun 2017
Also, here's the Matlab code if you are interested in taking a look.
KSSV on 7 Jun 2017
Edited: KSSV on 7 Jun 2017
It is easy,to achieve what you said. You are confused.

Precise Simulation on 7 Aug 2017
You can use the FEATool FEM toolbox and postprocessing function to plot unstructured FEM data on triangulated grids and meshes as described in the linked tutorial post.

Sanjay Kumar on 24 Apr 2023