Issue with contour plot due to different size

Hello,

As cited above I want to have a contour plot, but the problem is the size of X and Z are different. as given below:

x0 = x;
t0 = Time(1:9:100);
[t1, x1] = meshgrid(t0, x0);
contourf(t1,x1,H0I0_Turbulence_cen2,1000,'edgecolor','none')
colormap(jet);
colorbar;
 X = min(t0):(max(t0)-min(t0))/9:max(t0);

  set(gca, 'xlim', [min(t0) max(t0)]);

  set(gca, 'xtick', X);

 xtickformat('%.2f');
 xlabel('t','FontSize',24,'fontweight','bold');

  Y = min(x0):(max(x0)-min(x0))/9:max(x0);
 
  set(gca, 'ylim', [min(x0) max(x0)]);

  set(gca, 'ytick', Y);
  ytickformat('%.1f');
ytickformat('%.2f');
ylabel('x','FontSize',24,'fontweight','bold')

set(gca,'ycolor','k');
set(gcf,'color','w');
hold on
contour(t1,x1,H0I0_Turbulence_cen2,'k','ShowText','on')
grid on
hold off

ct = 0:(max(max(H0I0_Turbulence_cen2))-0)/10:max(max(H0I0_Turbulence_cen2));
c=colorbar('Ticks',ct);
clim([0 max(max(H0I0_Turbulence_cen2))]);
c.TickLabels = compose('%.2f',ct);
ylabel(c,'\itI_{cen}','FontSize',24, 'fontweight', 'bold');

Here, size(t1) = 100 x 12, size(x1) = 100x12,

and size(H0I0_Turbulence_cen2)=6x12

So size is differing by a large amount.

Thus I get the error as "Error using contourf

The size of X must match the size of Z or the number of columns of Z."

Is there any way to solve this issue and plot the contour?

[DGM]

What is the spatial relationship between them?

[Rahul]

hi,

thanks for the reply.

x0 denotes the position, t0 denotes the time, H0I0_Turbulence_cen2 whose dynamics is to be plotted as color graph.

But since H0I0_Turbulence_cen2 is 6x12 matrix, whereas t1 and x1 are 100x12 matrices, I wonder how to solve this problem.

[DGM]

That's what I'm asking you. Your X,Y grids are based off of:

x0 = x; % this creates 100 elements of YData
t0 = Time(1:9:100); % this creates 12 elements of XData

So the question is why the variable called "x" (which corresponds to y) has 100 elements when the Z data has 6. If there is some sort of interpolation or translation that needs to be done, where in the space of YData do the upper and lower rows of the Z data lie?

Answer 1

[Joshua Levin Kurniawan]

Here, the issue is that the size for using "contour" function is MATLAB must be comply as follows:

t0 must be equal to size(H0I0_Turbulence_cen2,2) and x0 must be a vector with length equal to size(H0I0_Turbulence_cen2,1). Or in other words, you can check

length(t0) == size(H0I0_Turbulence_cen2,2) %must return true
length(x0) == size(H0I0_Turbulence_cen2,1) %must return true

In this particular case, if you have x0 with length of 100 and t0 with length of 12, then contourf(t1,x1,H0I0_Turbulence_cen2,1000,'edgecolor','none') can be plotted if and only if H0I0_Turbulence_cen2 is 100x12 matrix

[DGM]

That's not how length() or contour() work. You're presuming that the inputs are vectors, when they clearly aren't. The X,Y inputs to contour() may either be vectors, or 2D grids. Length() returns the size of the largest dimension. Unless you know what you're doing with it, don't use it.

% these are valid inputs
[X Y] = meshgrid(linspace(0,1,10),linspace(0,1,100));
Z = X.^2 + Y.^2;

contour(X,Y,Z) % they work

% your tests will incorrectly declare that the inputs are invalid
length(X)

ans = 100

length(Y)

ans = 100

size(Z)

ans = 1x2

100 10

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The given X,Y inputs are 2D. The Z data is also 2D, but not the same size, and the sizes differ by a non-integer factor.