Why does my function output a series of answers that I don't want and have tried my best to supress

My code is as follows

function [T,Q]=osc_2
    tspan = [0: pi/20: 2*pi];

    qinit_1=[1;0];
    qinit_2=[0;1];
    
    [T,Q] = ode45(@osc,tspan,qinit_1);
    phi_1=[Q((end), 1); Q((end), 2)];
    
    [T,Q] = ode45(@osc,tspan,qinit_2);    
    phi_2=[Q((end), 1); Q((end), 2)];
    
    eigenvalues=eig([phi_1,phi_2]);
    Stability=eigenvalues(1,1)*eigenvalues(2,1)

end

with an accompanying second piece of code

function dqdt = osc(t,q)
    dqdt = zeros(2,1);
    a1=0;
    a2=2;
    a3=1;    
    dqdt(1) = q(2);
    dqdt(2) = -a1*q(2)-q(1)*(a2+a3*cos(t));
    
end

When I run the first function, it returns the stability as I want it to, but it also outputs the following

ans =

         0
    0.1571
    0.3142
    0.4712
    0.6283
    0.7854
    0.9425
    1.0996
    1.2566
    1.4137
    1.5708
    1.7279
    1.8850
    2.0420
    2.1991
    2.3562
    2.5133
    2.6704
    2.8274
    2.9845
    3.1416
    3.2987
    3.4558
    3.6128
    3.7699
    3.9270
    4.0841
    4.2412
    4.3982
    4.5553
    4.7124
    4.8695
    5.0265
    5.1836
    5.3407
    5.4978
    5.6549
    5.8119
    5.9690
    6.1261
    6.2832

Apologies for the length of the post, but is it possible to prevent the ans output from coming up? as far as I can tell it's simply giving the range of values used in tspan but I can't work out why it isn't supressed by the semicolon on that line.

I am very much new to MATLAB so simpler answers would be strongly prefered. I am also aware that there is most likely a different way of doing this as I only require the Q(end) values, however, this is the best I could do.

Answer 1

[Mehmed Saad]

Because its your function output

[T,Q] =osc_2

will give you two output which you specified

when you call

osc_2

the output will be T stored in ans and also will display on cmd

on the other hand you cannot see Stability in your workspace

removing a semi colon will display it on cmd but will not pass it out of the function

when you call

osc_2;

value of T will be stored in ans but it wont get displayed on cmd

[Kieran Corrigan]

Are you suggesting that I add a semicolon to the first line of the code i.e.

function [T,Q]=osc_2;

Because I have tried this and sadly it still displays ans in the command window and workspace

[Mehmed Saad]

when you call the osc_2 function in your script

[T,Q] = osc_2;

what you are doing is you are runing your function directly. dont do that. call it from the script

These 2 are your functions

function [T,Q]=osc_2
    tspan = [0: pi/20: 2*pi];
    qinit_1=[1;0];
    qinit_2=[0;1];
    
    [T,Q] = ode45(@osc,tspan,qinit_1);
    phi_1=[Q((end), 1); Q((end), 2)];
    
    [T,Q] = ode45(@osc,tspan,qinit_2);    
    phi_2=[Q((end), 1); Q((end), 2)];
    
    eigenvalues=eig([phi_1,phi_2]);
    Stability=eigenvalues(1,1)*eigenvalues(2,1)
end
function dqdt = osc(t,q)
    dqdt = zeros(2,1);
    a1=0;
    a2=2;
    a3=1;    
    dqdt(1) = q(2);
    dqdt(2) = -a1*q(2)-q(1)*(a2+a3*cos(t));
    
end

[Mehmed Saad]

% You can remove function from here though
    tspan = [0: pi/20: 2*pi];
    qinit_1=[1;0];
    qinit_2=[0;1];
    
    [T,Q] = ode45(@osc,tspan,qinit_1);
    phi_1=[Q((end), 1); Q((end), 2)];
    
    [T,Q] = ode45(@osc,tspan,qinit_2);    
    phi_2=[Q((end), 1); Q((end), 2)];
    
    eigenvalues=eig([phi_1,phi_2]);
    Stability=eigenvalues(1,1)*eigenvalues(2,1)

function dqdt = osc(t,q)
    dqdt = zeros(2,1);
    a1=0;
    a2=2;
    a3=1;    
    dqdt(1) = q(2);
    dqdt(2) = -a1*q(2)-q(1)*(a2+a3*cos(t));
    
end

[Kieran Corrigan]

Thank you that is perfect