Hello,
I’ve been following the following link — https://www.mathworks.com/help/optim/ug/fit-model-to-complex-data.html#
to try and extract the real constants (N_s,Tau_s, and c) from the Drude-Smith derivation for complex conductivity. This involves fitting both the real and imaginary components (which may be the problem in itself, since the example fits regular data with complex noise?)

I’ve attempted both lsqnonlin and lsqcurve fit methods.
file =[‘DSfit_Sitest.xls’]; %%file attached
input = xlsread(file);
x = input(:,1); %%%% xdata, freqency, omega, real numbers from (0.2-1.4 THz)
R = input(:,2); %%%% Real component (blue in plot)
I = input(:,3);%%%% Imaginary component (orange in plot)
ydata = complex(R,I); %%%% complex conductivity, sigma_s
q = 1.602E-19; %% charge
m = 0.98; %% effective electron mass
mi = 1/0.98; %% inverse electron mass used to make typing the equation simpler

objfcn = @(C)(((C(1)*(q^2)*mi*C(2))./(1-1i.*x.*C(2))).*(1+(C(3)./(1-1i.*x.*C(2))))) – ydata;
opts = optimoptions(@lsqnonlin,’Display’,’off’);
x0=[1e17, 100, -0.1]; %% initial guesses, I expect these to be reasonable values
LB = [1e15, 1, -1]; %%Typical carrier concentrations (cm-3), Tau_s (C(2)) units in picoseconds, -1<c<0
UB = [1e21, 1000, 0];
[const,~,residual,exitflag,output] = lsqnonlin(objfcn,x0,[],[],opts); %% does not run with LB and UB, so i leave blank.
This method outputs the initial guesses, and when I use the initial guesses to plot the outputs I get my data graph flipped, meaning my function just equals zero.
Using lsqcurvefit
objfcn = @(C,x)(((C(1)*(q^2).*mi.*C(2))./(1-1i.*x.*C(2))).*(1+(C(3)./(1-1i.*x.*C(2)))));
opts = optimoptions(@lsqcurvefit,opts);
x0=[1e17, 100, -0.1];
LB = [1e15, 1, -1];
UB = [1e21, 1e3, 0];
[constan,resnorm] = lsqcurvefit(objfcn,x0,x,ydata,[],[],opts)
I get the error "not enough input arguments" in my objfcn, and it still outputs the initial guesses

Any help with why this isnt working or if im doing something really wrong is greatly appreciated! I am a novice Matlab user.
Thank you!!Hello,
I’ve been following the following link — https://www.mathworks.com/help/optim/ug/fit-model-to-complex-data.html#
to try and extract the real constants (N_s,Tau_s, and c) from the Drude-Smith derivation for complex conductivity. This involves fitting both the real and imaginary components (which may be the problem in itself, since the example fits regular data with complex noise?)

I’ve attempted both lsqnonlin and lsqcurve fit methods.
file =[‘DSfit_Sitest.xls’]; %%file attached
input = xlsread(file);
x = input(:,1); %%%% xdata, freqency, omega, real numbers from (0.2-1.4 THz)
R = input(:,2); %%%% Real component (blue in plot)
I = input(:,3);%%%% Imaginary component (orange in plot)
ydata = complex(R,I); %%%% complex conductivity, sigma_s
q = 1.602E-19; %% charge
m = 0.98; %% effective electron mass
mi = 1/0.98; %% inverse electron mass used to make typing the equation simpler

objfcn = @(C)(((C(1)*(q^2)*mi*C(2))./(1-1i.*x.*C(2))).*(1+(C(3)./(1-1i.*x.*C(2))))) – ydata;
opts = optimoptions(@lsqnonlin,’Display’,’off’);
x0=[1e17, 100, -0.1]; %% initial guesses, I expect these to be reasonable values
LB = [1e15, 1, -1]; %%Typical carrier concentrations (cm-3), Tau_s (C(2)) units in picoseconds, -1<c<0
UB = [1e21, 1000, 0];
[const,~,residual,exitflag,output] = lsqnonlin(objfcn,x0,[],[],opts); %% does not run with LB and UB, so i leave blank.
This method outputs the initial guesses, and when I use the initial guesses to plot the outputs I get my data graph flipped, meaning my function just equals zero.
Using lsqcurvefit
objfcn = @(C,x)(((C(1)*(q^2).*mi.*C(2))./(1-1i.*x.*C(2))).*(1+(C(3)./(1-1i.*x.*C(2)))));
opts = optimoptions(@lsqcurvefit,opts);
x0=[1e17, 100, -0.1];
LB = [1e15, 1, -1];
UB = [1e21, 1e3, 0];
[constan,resnorm] = lsqcurvefit(objfcn,x0,x,ydata,[],[],opts)
I get the error "not enough input arguments" in my objfcn, and it still outputs the initial guesses

Any help with why this isnt working or if im doing something really wrong is greatly appreciated! I am a novice Matlab user.
Thank you!! Hello,
I’ve been following the following link — https://www.mathworks.com/help/optim/ug/fit-model-to-complex-data.html#
to try and extract the real constants (N_s,Tau_s, and c) from the Drude-Smith derivation for complex conductivity. This involves fitting both the real and imaginary components (which may be the problem in itself, since the example fits regular data with complex noise?)

I’ve attempted both lsqnonlin and lsqcurve fit methods.
file =[‘DSfit_Sitest.xls’]; %%file attached
input = xlsread(file);
x = input(:,1); %%%% xdata, freqency, omega, real numbers from (0.2-1.4 THz)
R = input(:,2); %%%% Real component (blue in plot)
I = input(:,3);%%%% Imaginary component (orange in plot)
ydata = complex(R,I); %%%% complex conductivity, sigma_s
q = 1.602E-19; %% charge
m = 0.98; %% effective electron mass
mi = 1/0.98; %% inverse electron mass used to make typing the equation simpler

objfcn = @(C)(((C(1)*(q^2)*mi*C(2))./(1-1i.*x.*C(2))).*(1+(C(3)./(1-1i.*x.*C(2))))) – ydata;
opts = optimoptions(@lsqnonlin,’Display’,’off’);
x0=[1e17, 100, -0.1]; %% initial guesses, I expect these to be reasonable values
LB = [1e15, 1, -1]; %%Typical carrier concentrations (cm-3), Tau_s (C(2)) units in picoseconds, -1<c<0
UB = [1e21, 1000, 0];
[const,~,residual,exitflag,output] = lsqnonlin(objfcn,x0,[],[],opts); %% does not run with LB and UB, so i leave blank.
This method outputs the initial guesses, and when I use the initial guesses to plot the outputs I get my data graph flipped, meaning my function just equals zero.
Using lsqcurvefit
objfcn = @(C,x)(((C(1)*(q^2).*mi.*C(2))./(1-1i.*x.*C(2))).*(1+(C(3)./(1-1i.*x.*C(2)))));
opts = optimoptions(@lsqcurvefit,opts);
x0=[1e17, 100, -0.1];
LB = [1e15, 1, -1];
UB = [1e21, 1e3, 0];
[constan,resnorm] = lsqcurvefit(objfcn,x0,x,ydata,[],[],opts)
I get the error "not enough input arguments" in my objfcn, and it still outputs the initial guesses

Any help with why this isnt working or if im doing something really wrong is greatly appreciated! I am a novice Matlab user.
Thank you!! complex curve fitting, curvefitting, lsqcurvefit, lsqnonlin, complex data, drude-smith MATLAB Answers — New Questions

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