Error using surf (line 71) Z must be a matrix, not a scalar or vector.

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Noob 2024-12-30

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https://ww2.mathworks.cn/matlabcentral/answers/2172576-error-using-surf-line-71-z-must-be-a-matrix-not-a-scalar-or-vector

评论： Walter Roberson 2025-1-3

采纳的回答： Torsten

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Hi there!

I currently have a tiledLayout plot with six tiles; the tiles are plotted against two variables alpha and beta, and I am using the x-axis for alpha, and colors for beta (using a colormap). Now I want to experiment with a 3D surface plot, using the x- and y-axes for alpha and beta. However, when I run the code

[alpha, beta] = meshgrid(alpha,beta);
surf(alpha,beta,FL_hat);

I am getting the error message that FL_hat must be a matrix, not a scalar or vector.

How can I fix this bug?

In my code, I loop through beta, but I set alpha = linspace(0, 2*pi, 1001), for example.

So, I tried not looping through beta, and just setting beta = linspace(0, 2*pi,1001), but that didn't seem to help.

I also tried using the contour3 function, writing:

[alpha, beta] = meshgrid(alpha,beta);
contour3(alpha,beta,FL_hat);

but then I get the error message, "Error using contour3 (line 44) Z must be at least a 2x2 matrix."

Thanks in advance,

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Walter Roberson 2024-12-30

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The problem is that FL_hat is not a 2D array with at least 2 elements in each of the dimensions.

Looping through beta is not a problem, provided you use a structure similar to

for beta_index = 1 : number_of_betas
    current_beta = beta(beta_index);
    FL_hat(beta_index, :) = values_calculated_from_current_beta_and_alpha;
end

Noob 2024-12-30

编辑：Noob 2024-12-30

Hi @Walter Roberson! My little FL_hat function is in a separate function file, where beta doesn't show up.

Beta only shows up in my data-plotting file, where I use it to vary the actual model inputs to FL_hat, and then make figures.

While beta is not an actual model input, it is an important parameter for my work, so I wanted to plot FL_hat against alpha, an actual model input, and beta, not a model input, but an important descriptive parameter.

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