2D contour plot with given matrix

I would like to create a contour plot for a heat transfer application, where the values of the matrix are nodal temperature values over the 2d domain of (x 0 to 0.5) and (y 0 to 1). Using the following values

25, 25, 25

111.5, 137.8, 245.1

146.3, 178.3, 296.4

111.5, 137.8, 245.1

25, 25, 25

Where, nodes are seperated by 0.25 (i.e the value at (0.5,0.5) is 296.4).

Please provide the generated plot to ensure the generated codes is functioning.

Answer 1

[Star Strider]

Two possibilities —

M = [25, 25, 25
111.5, 137.8, 245.1
146.3, 178.3, 296.4
111.5, 137.8, 245.1
25, 25, 25];

figure
contour(M)

figure
contourf(M)

.

[David Krouse]

Is there a way to plot it on the physical domain of the problem. Where, the x axis would range from 0 to 0.5 and the y axis would range from 0 to 1?

[Star Strider]

The contour plot data can be difficult to work with, especially (as here) specific levels are not continuous. It would likely be easier to scale the physical domain of the problem to the contour and adjust the axis tick labels.

What is the physical domain of the problem?

.

[David Krouse]

A 2d rectangular solid of dimension 0.5 by 1

[Star Strider]

That would be relatively straightforward.

M = [25, 25, 25
    111.5, 137.8, 245.1
    146.3, 178.3, 296.4
    111.5, 137.8, 245.1
    25, 25, 25];

xv = linspace(0, 0.5, size(M,2));
yv = linspace(0, 1.0, size(M,1));

figure
contour(xv,yv,M)
axis('equal')                               % Optional

figure
contourf(xv,yv,M)
axis('equal')                               % Optional

Since I’m not certain how the ‘xv’ and ‘yv’ vectors correspond to the ‘M’ matrix, it might be necessary to re-define them in terms of the dimeensions of ‘M’ if I guessed wrong. However, re-scaling them is straightforward.

Also, with axis('equal') there seems to be a bug in the x-axis ticks here, although it could just be a problem with the online Run feature, since it doesn’t appear when I run the same code offline on my computer (although the tick label at 0.5 still fails to plot). That can be fixed manually if necessary.

.