I am getting an error using interp1

I have table of n and k vs frequency for TiO2 and I am trying to plot the corresponding dielectrics. Here is the code

    function [frequency, dielectric_function] = plot_optical_constants_TiO2(n);
    color_1 = [0.7411, 0, 0.1490];
    color_2 = [0.9412, 0.2314, 0.1255];
    color_3 = [0.9922, 0.5529, 0.2353];
    color_4 = [0.9961, 0.8, 0.3608];
    color_5 = [1, 1.0, 0.3980];
    set(0,'defaultaxesfontsize',20);
    set(0,'defaulttextfontsize',20);
    set(0,'defaultaxeslinewidth',2);
    set(0,'defaultlinemarkersize',10);
    set(0,'DefaultFigureWindowStyle','docked');
    set(0,'DefaultFigurePosition', [0         918         1120         840]);
    
    N_w = 1000 ;             % number of points in frequency span
    N_k = 2000 ;         	% number of points in wavevector span
    
    w_min = 5E12;
    w_max = 1e15;
    [w,k_r] = ndgrid( (linspace(w_min,w_max,N_w)) , (linspace(0,50E6,N_k)) );
    e_TiO2 = dlmread('e_TiO2.txt');
    w_Ge = e_TiO2(:,1);
    e_TiO2 = e_TiO2(:,2) + 1i*e_TiO2(:,3);
    e_TiO2_interp = interp1(w_Ge, e_TiO2, w);
    dielectric_function = e_TiO2_interp;
    frequency = w(:,1);
    figure(4)
    hh = plot(w(:,1), real(e_TiO2_interp(:,1)),w(:,1), imag(e_TiO2_interp(:,1)));
    legend('\epsilon''_{TiO2}', '\epsilon''''_{TiO2}')
    ylabel('Dielectric Function')
    xlabel('Frequency, {\omega} (rad/s)')
    set(hh(1), 'color', color_3)
    set(hh(2), 'color', color_1)
    xlim([5e12 1e15])
end

The error is pasted below:

Error using matlab.internal.math.interp1

Sample points must be unique.

Error in interp1 (line 188)

VqLite = matlab.internal.math.interp1(X,V,method,method,Xqcol);

Error in plot_optical_constants_TiO2 (line 24)

e_TiO2_interp = interp1(w_Ge, e_TiO2, w);

[Catalytic]

It looks like only a fragment of the error message was pasted.

[Matt J]

Yes, and also only a fragment of the code. We don't know with what value of n, the function was called.

[Ambali Odebowale]

This is the complete error

Error using matlab.internal.math.interp1

Sample points must be unique.

Error in interp1 (line 188)

VqLite = matlab.internal.math.interp1(X,V,method,method,Xqcol);

Error in plot_optical_constants_TiO2 (line 24)

e_TiO2_interp = interp1(w_Ge, e_TiO2, w);

[Image Analyst]

@Ambali Odebowale, did you see Matt's reply? It looks like you overlooked the last line "We don't know with what value of n, the function was called" So, how did you call it? Did you call it like

[frequency, dielectric_function] = plot_optical_constants_TiO2(1000)

or what? Again, what is n? You didn't just click the green run triangle without assigning a value of n did you? Because that would cause an error.

And where is n even used inside the function?

[Voss]

@Ambali Odebowale I think it will be useful if you attach the file e_TiO2.txt as well.

[Ambali Odebowale]

Here is the attached file. Thanks

[Yordani]

Hello Ambali I would like to contact you to discuss this code designed for NFRHT. Can you give me your cell phone number or email? Thank you

[Ambali Odebowale]

[e-mail]

Answer 1

[DGM]

Strip out all the multiply-defined points:

color_1 = [0.7411, 0, 0.1490];
color_2 = [0.9412, 0.2314, 0.1255];
color_3 = [0.9922, 0.5529, 0.2353];
color_4 = [0.9961, 0.8, 0.3608];
color_5 = [1, 1.0, 0.3980];
set(0,'defaultaxesfontsize',20);
set(0,'defaulttextfontsize',20);
set(0,'defaultaxeslinewidth',2);
set(0,'defaultlinemarkersize',10);
set(0,'DefaultFigureWindowStyle','docked');
set(0,'DefaultFigurePosition', [0         918         1120         840]);

N_w = 1000 ;             % number of points in frequency span
N_k = 2000 ;         	% number of points in wavevector span

w_min = 5E12;
w_max = 1e15;
[w,k_r] = ndgrid( (linspace(w_min,w_max,N_w)) , (linspace(0,50E6,N_k)) );
e_TiO2 = dlmread('TiO2.txt');
w_Ge = e_TiO2(:,1);
[w_Ge uidx] = unique(w_Ge);
e_TiO2 = e_TiO2(:,2) + 1i*e_TiO2(:,3);
e_TiO2 = e_TiO2(uidx);
e_TiO2_interp = interp1(w_Ge, e_TiO2, w);
dielectric_function = e_TiO2_interp;
frequency = w(:,1);
figure(4)
hh = plot(w(:,1), real(e_TiO2_interp(:,1)),w(:,1), imag(e_TiO2_interp(:,1)));
legend('\epsilon''_{TiO2}', '\epsilon''''_{TiO2}')
ylabel('Dielectric Function')
xlabel('Frequency, {\omega} (rad/s)')
set(hh(1), 'color', color_3)
set(hh(2), 'color', color_1)
xlim([5e12 1e15])

[Ambali Odebowale]

@DGM Great! Thanks