Why this equation cannot be fitted?

2020 1 15
1 个回答
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更新时间：2020 1 15
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I'm trying to fit the function below:
fitfunction = strcat('l*x*z+l*y*z');
myfittype = fittype(fitfunction,...
'dependent',{'f'},'independent',{'x','y','z'},...
'coefficients',{'l'});
However, Matlab wouldn't allow me to creat the fittype. The error message here:
"Expression l*x*z+l*y*z is not a valid MATLAB expression, has non-scalar coefficients, or cannot be evaluated:
Not enough inputs to FITTYPE function."
Does anybody know why this happened? Thanks!

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 采纳的回答

Walter Roberson
Walter Roberson 2020-1-15

0 个投票

You cannot use 3 or more independent variables.
f = l*(x+y)*z
Implies
f/(z*(x+y)) = l
Which becomes the defining estimate with the understanding that / is the matlab matrix division operation

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