lsqcurvefit is undefined in MathLab version R2007b

Hello MathLab community,

I have copied follwong code from MathWorks example:

xdata = ...

[0.9 1.5 13.8 19.8 24.1 28.2 35.2 60.3 74.6 81.3];

ydata = ...

[455.2 428.6 124.1 67.3 43.2 28.1 13.1 -0.4 -1.3 -1.5];

fun = @(x,xdata)x(1)*exp(x(2)*xdata);

x0 = [100,-1];

x = lsqcurvefit(fun,x0,xdata,ydata)

Running this code gives following error:

??? Undefined function or method 'lsqcurvefit' for input arguments of type 'function_handle'.

Error in ==> Fitt_2 at 11

x = lsqcurvefit(fun,x0,xdata,ydata)

What is the problem in the code?

Can anybody help to solve?

I'm working with MathLab version R2007b.

Thank you.

[Rik]

Did you make sure to install the appropriate toolbox? The doc page states it was introduced before R2006a, so it did exist.

[Matt J]

Lieu-Kim Dang comment moved here:

Hello Rik,

thank you for your advice. Which toolbox is needed?

[Max Heimann]

It seems to be part of the optimization toolbox.

https://mathworks.com/help/optim/ug/lsqcurvefit.html

Answer 1

[Mathieu NOE]

hello

FYI, you can do basic curve fitting with fminsearch - without the optimization toolbox

clc
clearvars

x =  [0.9 1.5 13.8 19.8 24.1 28.2 35.2 60.3 74.6 81.3];
y =  [455.2 428.6 124.1 67.3 43.2 28.1 13.1 -0.4 -1.3 -1.5];


f = @(a,b,x) a.*exp(b.*x);
obj_fun = @(params) norm(f(params(1), params(2),x)-y);
sol = fminsearch(obj_fun, [0,0]);
a = sol(1);
b = sol(2);

xfit = linspace(min(x),max(x),100);
yfit = f(a, b, xfit);

figure;
plot(x, y, '+', 'MarkerSize', 10, 'LineWidth', 2)
hold on
plot(xfit, yfit, '-');

TE = sprintf('C = %0.2fe^{%0.3ft}',a, b);
text(x(3), y(3)*1.5, TE);

[Rik]

You do need to be aware that fminsearch is more sensitive to local minima than many other fitters in Matlab, or so I've heard.

[Mathieu NOE]

For those who want to go beyond fminsearch but still lack the optimization toolbox :

Fminspleas - File Exchange - MATLAB Central (mathworks.com)

Answer 2

[Lieu-Kim Dang]

Hello Mathieu,

many thanks for your valuable solution. I will try it out.

[Mathieu NOE]

my pleasure !

Answer 3

[Lieu-Kim Dang]

Hello Max,

thank you for your information. I'm contacting MAthLab to get the license for this toolbox.

[Rik]

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