Plotting a function within for loop

Hello,

Im trying to plot the theta value in my file for the values of the index. How can I plot all the results on a single plot rather than have the plot only show the result for each specific iteration?

Thank you

Answer 1

[David Hill]

function RetractionModel2

AB = 0.0732;
AD = 0.0788;
BC = 0.0585;
CD = 0.0575;
a0 = 99.4;


for i= 0:90

alpha = a0 - i;
BD = sqrt(AB^2+AD^2-2*AB*AD*cosd(alpha));
delta = asind((AB./BD).*sind(alpha));
beta = 180 - alpha - delta;

psi = acosd((BD.^2+CD^2-BC.^2)/(2*BD*CD));
zeta = asind((CD/BC)*sin(psi));
phi = beta - zeta;
theta(i+1) = delta - psi; %need to index

end
plot(0:90,theta);

end

[Leandro Seguro]

Thanks a lot!

Answer 2

[William Rose]

Your function does not assign a value to the output variable "output".

I suggest you initialize vectors theta and phi inside the funciton, before the for loop. Then populate those vectors, one element at a time, during each loop pass. Then return those vectors from the function to the calling program (such as main.m). Then plot each vector in the calling program. See attached example.

%main.m
%Leandro Seguro & W.Rose
[theta,phi]=RetractionModel2;
figure;
subplot(2,1,1); plot(0:90,theta,'rx-');
title('RetractionModel2');
ylabel('Theta');
subplot(2,1,2); plot(0:90,phi,'rx-');
xlabel('i'); ylabel('Phi');

The modified function is below. Take note of what is different.

function [theta,phi] = RetractionModel2(~)
%This function returns vectors theta and phi.

AB = 0.0732;
AD = 0.0788;
BC = 0.0585;
CD = 0.0575;
a0 = 99.4;

phi=zeros(91,1);        %initialize phi vector
theta=zeros(91,1);      %initialize theta vector

for i= 0:1:90
    alpha = a0 - i;
    BD = sqrt(AB^2+AD^2-2*AB*AD*cosd(alpha));
    delta = asind((AB./BD).*sind(alpha)) ;
    beta = 180 - alpha - delta;
    psi = acosd((BD.^2+CD^2-BC.^2)/(2*BD*CD));
    zeta = asind((CD/BC)*sin(psi));
    phi(i+1) = beta - zeta;
    theta(i+1) = delta - psi; 
end

end

Minor comment: I added semicolons to suppress the display of the intermediate results in the function.