Undefined variable or function 'f'

Question

Allen Zhong 2020-1-19

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/500995-undefined-variable-or-function-f

回答： Kaashyap Pappu 2020-1-23

Hi, I'm trying to resolve an error in my matlab code, which is trying to find the inductance and resistance through voltage and current. Here are my codes:

function [b,m,db,dm] = wRegression(x, y, dy)

% WREGRESSION [b,m,db,dm] = wRegression(x, y, dy)

% Written by: Allen Zhong

% takes x and y values, and uncertainies on y (dy), and outputs the slope

% (m), intercept (b), slope error (dm), and intercept error (db) for the

% linear regression (y = mx + b)

%define the variable w to simplify expressions

w = 1./(dy.^2);

D = addUp(w).*addUp(w.*x.^2)-(addUp(w.*x)).^2;

b = (addUp(w.*x.^2).*addUp(w.*y)-addUp(w.*x).*addUp(w.*x.*y))/D; %Computes y intercept

m = (addUp(w).*addUp(w.*x.*y)-addUp(w.*x).*addUp(w.*y))/D; %Computes slope

db = sqrt(addUp(w.*x.^2)/D); %Computes uncertainties in intercept

dm = sqrt(addUp(w)/D); %Computes uncertainties in slope

end

function [L, R, dL, dR] = findInductanceAndResistance(f, V, I, dV, dI)

wsq = (2.*pi.*f).^2;

Z2 = (V./I).^2;

dzSqrd = ((Z2(V+dV,I)-Z2(V,I)).^2+(Z2(V,I+dI)-Z2(V,I)).^2).^0.5;

[Rsq,Lsq,dLsq,dRsq] = wRegression(wsq,Z2,dzSqrd);

L= (Lsq).^0.5;

R = (Rsq).^0.5;

dR = (Rsq+dRsq).^0.5-(Rsq).^0.5;

dL = (Lsq+dLsq).^0.5-(Lsq).^0.5;

end

For 'findInductanceAndResistance', I can't seem to get it working as there is always an unresolved 'undefined function 'f''. Any help and assistance would be appreciated.

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Star Strider 2020-1-19

Siunce ‘f’ is an agrument (that appears to be a frequency vector), it must specifically be passed to the function. Functions written using the function declaration (as opposed to anonymous functions) do not inherit variables from the workspace.

Stephan 2020-1-19

How do you call this function?

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Answer 1

Kaashyap Pappu 2020-1-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/500995-undefined-variable-or-function-f#answer_411583

The variable ‘f’ needs to be passed as an input argument in the function call. As has been mentioned, each function has its own workspace and therefore will not access variables from the base workspace. More information can be found here.

If ‘f’ is a custom function, you may have to make sure the function is saved in the same directory while calling ‘findInductanceAndResistance’.

Hope this helps!

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