Contour plot over a specified region

Hi, I want to do a contour plot over a speciefied region, for example a triangle or a 4-node element. These 4 node locations do NOT form a rectangle.

Answer 1

[Karim]

Using the patch command u can plot as many triangular or rectangular shapes at the same time.

Just build the grid (i.e. the 'vertices') and the a conectivity matrix (i.e. 'faces') to connect selected points from the grid.

% create a random grid
MyGrid = [-3.01 -2.82;  % node 1
           1.33 -1.31;  % node 2
           0.70  1.79;  % node 3
          -2.46  2.46]; % node4

figure
subplot(1,2,1)
patch('Faces', [1 2 3 4], 'Vertices', MyGrid,'FaceColor','none')
grid on
subplot(1,2,2)
patch('Faces', [1 2 4], 'Vertices', MyGrid,'FaceColor','none')
grid on

[Claus E. Jebens]

Thanks, however my question is how to do a countour plot over an arbitraray region defined by 3, 4 .. nodes. In particular I want to plot the shape function n(x,y) of the triange, quad over the element area. Data, like n(x,y) , sigma(x,y), temperature (x,y) ... are defined only whithin the element area.