Matlab code - probably a simple mistake

I am trying to calculate kx, and ky. The conductivity in the x and y direction. The graph is supposed to look like a nice upwards curve, however mine fluxuates up and down(like a wave). I have checked my formulas, by inserting the values into the equation for L, the values of kx and ky appear to be correct. It seems as though the graphing part does not work tho.

I am going from L is 30 to 140, increments of 10. This is the only variable that changes. Here is my code:

clear
clc
% Constants

mfp = 31;           % mean free path (nm)
k = 316.72;         % conductivity (W / m*k)

% Equations

Lmax = 140;
dL=10;
L=30;

while L<=Lmax

kx(L)=k*(1-((2*mfp)/(3*3.14*L)));

ky(L)=k*(1-(mfp/(3*L)));

L= L+dL;

end

plot(kx,'-'),hold on, plot(ky,'--'), hold on, plot(k);
title(['Conductivity ']);
xlabel('Thickness (nm)','FontSize',14);
ylabel('Conductivity','FontSize',14);
leg1=legend('kx','ky');

Answer 1

[Paulo Silva]

You are just looking for plot(kx,ky) not all those plots

Also the calculations generate several zero values, that's why plot(kx,ky) shows many lines, you can plot just their values plot(kx,ky,'*') or ignore all the zeros and connect the points with one line:

clear
clc
% Constants
mfp = 31;           % mean free path (nm)
k = 316.72;         % conductivity (W / m*k)
% Equations
Lmax = 140;
dL=10;
L=30;
while L<=Lmax
kx(L)=k*(1-((2*mfp)/(3*3.14*L)));
ky(L)=k*(1-(mfp/(3*L)));
L= L+dL;
end
kx(~kx)=[];
ky(~ky)=[];
plot(kx,ky);
title(['Conductivity ']);
xlabel('Thickness (nm)','FontSize',14);
ylabel('Conductivity','FontSize',14);

[Chris]

I am letting the while loop, go from 30 to 140. While computing values for kx, and ky . I am able to plot kx and ky, however, the plots are identical. However, when you manually solve the equations, they are not the same ( like it should be) . I am trying to plot kx and ky, dont worry about the extra plot for k.

[Chris]

I am not by matlab right now, but what exactly is this doing now,

kx(~kx)=[];

ky(~ky)=[];

[Paulo Silva]

that removes the zeros from the kx and ky vectors so you can get one line connecting all non zero points, I don't know if the results are correct that way, please check if they are correct, the line is there and it goes up like you said.

[Chris]

when you say removes all the zeros, are you referring to all the zeros from 0 to about 30? This just makes the graph from 30 to 140 now? is that what you mean?

It should look like the graph of square root of x to a degree

[Paulo Silva]

I don't know where the zeros are, I just noticed that they are messing up the result of the plot function and yes the result does look like plot(x,sqrt(x))