Function file not behaving

Question

Thomas Humphrey 2012-1-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/26037-function-file-not-behaving

评论： Michael 2024-2-7

采纳的回答： Wayne King

在 MATLAB Online 中打开

When trying to run this function, every time it comes up with an error which I'm not sure where it is.

I'm calling it using the code, and getting the error:

[BPE] = BPE(T_f, X_f)

And I'm getting these errors:

??? Attempted to access BPE(69.81,42); index must be a positive integer or logical.
?? Index exceeds matrix dimensions
??? Attempted to access BPE(69,42); index out of bounds because numel(BPE)=1.

T_f = 69.81 and X_f = 42

This is my function file:

function [BPE] = BPE(T, X)
% A function to calculate The Boiling point elevation in degrees Celcius
A = (8.325e-2 + 1.883e-4 * T + 4.02e-6 * T^2);
B = (-7.625e-4 + 9.02e-5 * T - 5.2e-7 * T^2);
C = (1.522e-4 - 3e-6 * T - 3e-8 * T^2);
BPE = 100 * A*X + B*X^2 + C*X^3;
end

Any thoughts as to why this is failing?

Thanks in advance.

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Michael 2024-2-7

Anyone please clarify to me what T are we using in the below function?

function [rise] = BPRfunc(T,x)

A = (8.325e-2 + 1.883e-4*T + 4.02e-6*T.^2);

B = (-7.625e-4 + 9.02e-5 * T - 5.2e-7 * T.^2);

C = (1.522e-4 - 3e-6 * T - 3e-8 * T.^2);

rise = A*x + B*x^2 + C*x^3;

end

If it is the boiling point temperature of the feed water (seawater), isn't it dependent on BPE? Is it a scalar value?

Also, I think T changes with effect number?

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Answer 1

Wayne King 2012-1-13

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/26037-function-file-not-behaving#answer_34026

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Don't name your output variable the same as the function. Because after you output BPE once, then it's a variable in the workspace and you subsequently try to access a non-integer element of a variable (a scalar in this case).

Change the name of the output argument in your function.

function [BP] = BPE(T, X)
% A function to calculate The Boiling point elevation in degrees Celcius
A = (8.325e-2 + 1.883e-4 * T + 4.02e-6 * T^2);
B = (-7.625e-4 + 9.02e-5 * T - 5.2e-7 * T^2);
C = (1.522e-4 - 3e-6 * T - 3e-8 * T^2);
BP = 100 * A*X + B*X^2 + C*X^3;
end