fun(@x)
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Hi,
I have a semilog graph which must be fitted (in its linear region) using this equation: y = 6e17*B*log[(x+B)/B]
Can you please tell how can I obtain the value of constant B, using fun(@x) ?
Thank you so much in advance for your help !
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Ameer Hamza
on 26 Jun 2018
Edited: Ameer Hamza
on 26 Jun 2018
If you have a vector of x and y values then you can use several functions to estimate B. The correct method to use depending on your definition of the error function. For example, if you want to estimate B by minimizing the MSE (mean square error) then use lsqcurvefit(). For example,
xdata = ...; % vector of x values
ydata = ...; % vector of y values
y = @(B, x) 6e17*B.*log((x+B)./B);
B_estmated = lsqcurvefit(y, 1, xdata, ydata);
^ initial point for the numerical optimization algorithm.
Similarly, if you have some other error function, then you can use fmincon().
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Ameer Hamza
on 27 Jun 2018
Yes, this equation will give the predicted output y. Also, I realize that using one y together in one statement can be a bit confusing but this syntax is correct. MATLAB does not confuse both y's with each other. You can change either one of the y to another variable name to avoid confusion.
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