Sudden error "Unidentified function or variable"

Question

Kyle Dalminton 2021-7-26

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/885799-sudden-error-unidentified-function-or-variable

评论： DGM 2021-7-26

Hello everyone

I've got a problem when trying to run a code today. While the code ran perfectly yesterday, it only showed "Unidentified function or variable" today. Can anybody help me with this? Thank you very much.

My code:

[X1 Y1] = Elispe(1, sqrt(4/3), 0, 0, 0, 2*pi);
Z1 = zeros(1, length(X));
Z2 = ones(1, length(X));
X = [X1;X1];
Y = [Y1;Y1];
Z = [Z1;Z2];
%figure
Purple = [0.5,0,1]
surface(X,Y,Z, 'EdgeColor',Purple);
function [X Y] = Elispe(r1,r2, h, k, a, b) 
    t = linspace(a, b, 50);
    X = r1*cos(t) + h;
    Y = r2*sin(t) + k;
end

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Answer 1

DGM 2021-7-26

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https://ww2.mathworks.cn/matlabcentral/answers/885799-sudden-error-unidentified-function-or-variable#answer_753749

编辑：DGM 2021-7-26

在 MATLAB Online 中打开

Did you read what the error message said?

Unrecognized function or variable 'X'.

Error in untitled (line 3)

Z1 = zeros(1, length(X));

So what is X? Is it X1?

Z1 = zeros(1, length(X1));
Z2 = ones(1, length(X1));

I imagine the only reason this once worked was because there was a volatile copy of X just floating around in the workspace -- probably left over from when you changed variable names or something.

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Kyle Dalminton 2021-7-26

Ah I see, thank you for pointing this out. I was panic since it worked perfectly last night. It makes me wonder why X1 suddenly disappeared? Anyway, thank you and have a good day.

DGM 2021-7-26

It happens. When building stuff in a sandbox, it's helpful to run clearvars at least every now and then to make sure your code isn't relying on ephemeral variables that aren't being set by the current version of the code. If things are going to break, it's best they break while you still have your eyes and mind on it.

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