Error using contourf Z must be at least a 2x2 matrix. Error in D18071 (line 106) contourf(st)

Question

Mohd Babar 2024-7-18

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https://ww2.mathworks.cn/matlabcentral/answers/2138371-error-using-contourf-z-must-be-at-least-a-2x2-matrix-error-in-d18071-line-106-contourf-st

回答： Mohd Babar 2024-7-31

Hi, I am trying to create contour plot but after trying many times I am getting the same error, can anyone tell me what I am doing wrong in the code

*The code is*

s su = round(4*d/g)+1 ;

r = E((((su-1)- round(d/g)):-1:1),(su-1));

p = E((((su-1)- round(d/g)):-1:1),(su));

st = (p+r)./(1.5*(10)^(-4));

m = g*(size(r)-1);

H = 0:g:(m);

h = H./10;

writematrix(st)

type 'st.txt'

writematrix(h)

type 'h.txt'

plot(h,st)

xlim([0 1.5])

xlabel("X2/d",'fontsize',14)

ylabel("Normalised Strain along vertical path", 'fontsize',13)

legend("d/w = 0.5")

saveas(gcf,'plot.png')

contourf(st)

colorbar

saveas(gcf,'contour.png')

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Answer 1

Sivsankar 2024-7-18

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编辑：Sivsankar 2024-7-18

在 MATLAB Online 中打开

Hi Babar,

It seems that the error arises from the line

contourf(st)

The function expects you to send at least a 2x2 matrix as the argument. The error message suggests that Z is the argument, and it must be a function of two variables. In your case the argument is ‘st’.

From your code I can notice that the value of ‘st’ depends on ‘p’ and ‘r’ which in turn depend on the ‘E’ function. So, try to verify the value of ‘st’before passing it to the ‘contourf’ function and make sure it is a function of two variables, i.e, a 2x2 matrix or more.

You can also leverage the documentation on the ‘contourf’ function:

https://www.mathworks.com/help/matlab/ref/contourf.html

Thanks.