Plot finite element method using Matlab

Suppose that I have triangular mesh as follows:

and the mesh data structure is like

element = [nodeTag1 nodeTag2 nodeTag3];

coordinate = [x1, y1
    x2, y2
    x3, y3]; % coordinates of each node

I can use

patch('Vertices', coordinate, 'Faces', element)

to plot the mesh (the above plot).

After FEM analysis, I can get the values at each node (vertices of each triangle), like

data = [p1, p2, p3];

To plot the field, I can use

patch('Vertices', coordinate, 'Faces', element, 'FaceVertexCData', Data, 'FaceColor', 'interp');

to interpolate the values (field) on such a domain, with a colormap, and the results is like the following plot

My questions are

1. If I can only get the values on the each edge of triangles (i.e. centers of edges), how can I plot the result?
2. If I can only get the values on the center of triangles, how to plot the result?

Besides, the domain can be very irregular. I am affrid that

contourf

and

 meshgrid

are not applicable.

Answer 1

[KSSV]

You can interpolate the values to a grid using griddata or scatteredInterpolant. Read about them.

You can also plot contours using the present data. For this refer: https://in.mathworks.com/matlabcentral/fileexchange/38858-contour-plot-for-scattered-data