MATLAB: It says “too many output arguments” when I try to run the function. Why

argumenterrorfunctionMATLABoutput

The function has worked great till I added the xm and ym output arguments (and the "if" structure). Why does this occur now?
function [glongitude, date, longitude, latitude, gpt, xm, ym] = GroundTrack(VettXs, ...
    VettYs, VettZs, omegarot, dt, Nt, RT)
[longitude, latitude, ~] = cart2sph(VettXs, VettYs, VettZs);
longitude = longitude(:);                        % expressed in radians
latitude = latitude(:);
tom = evalin('base', 'tom');                     % identifies the type of map
alphadate = evalin('base', 'alphadate');
d = evalin('base', 'd'); ds = string(d);
date = strings(Nt);                        
gpt = nan(Nt, 3);                          
date(1) = ds; date(2) = date(1);               
% Till the "MOLLWEIDE PROJECTION" section a simple conversion from cartesian
% coordinates to polar coordinates is implemented. This conversion is
% then used to obtain longitude (glongitude) and latitude of the projection on Earth of
% the satellite's position. From longitude and latitude is then possible to
% get all the coordinates of the ground track on other maps obtained with
% other cartographical projections.
modulus = sqrt(VettXs(2)^2 + VettYs(2)^2 + VettZs(2)^2);
gpt(1, :) = 0;
gpt(2, 1) = VettXs(2)*RT/modulus; gpt(2, 2) = VettYs(2)*RT/modulus; 
gpt(2, 3) = VettZs(2)*RT/modulus; 
it = seconds(dt);
glongitude = nan(Nt, 1); 
glongitude(1) = 0;
glongitude(2) = longitude(2) - alphadate;
n = glongitude(2)/(2*pi);                       % number of complete turns
if (n - floor(n)) <= 0.5                        
    glongitude(2) = 2*pi*(n - floor(n));
    glongitude(2) = glongitude(2)*180/pi;
else
    glongitude(2) = -2*pi*(1 - (n - floor(n)));
    glongitude(2) = glongitude(2)*180/pi;
end
for i = 3 : Nt
    beta = omegarot*dt*(i-2);
    glongitude(i) = longitude(i) - beta - alphadate;
    n = glongitude(i)/(2*pi);
    d = d + it; ds = string(d); date(i) = ds;
if (n - floor(n)) <= 0.5                         
    glongitude(i) = 2*pi*(n - floor(n));
    glongitude(i) = glongitude(i)*180/pi;
else
    glongitude(i) = -2*pi*(1 - (n - floor(n)));
    glongitude(i) = glongitude(i)*180/pi;
end
    modulus = sqrt(VettXs(i)^2 + VettYs(i)^2 + VettZs(i)^2);
    gpt(i, 1) = VettXs(i)*RT/modulus;
    gpt(i, 2) = VettYs(i)*RT/modulus;
    gpt(i, 3) = VettZs(i)*RT/modulus;
end
% MOLLWEIDE PROJECTION
if (tom == 2)
    teta = nan(length(latitude), 1);
    xm = nan(length(longitude), 1);
    ym = nan(length(latitude), 1);
    % Iterative cycle
    for i = 1 : Nt
        % First step
        tetaf = latitude(i);
        dtetaf = -(tetaf + sin(tetaf) - pi*sin(latitude(2)))/(1 + cos(tetaf));
        % Other steps
        while abs(dtetaf) >= 1e-6
            dtetaf = -(tetaf+sin(tetaf)-pi*sin(latitude(i)))/(1+cos(tetaf));
            tetaf = tetaf + dtetaf;
        end
        teta(i) = tetaf/2;
        xm(i) = (RT*2*sqrt(2)/pi)*(glongitude(i)-glongitude(2))*cos(teta(i));
        ym(i) = RT*sqrt(2)*sin(teta(i));
    end
end
end

Best Answer

Hi,
if you change the number of output arguments of a function, make sure to that the number of output arguments in your function call is equal or less then the number of output arguments defined in your function. Otherwise you get this error.
Consider this example function:
function [a, b] = fun(f1, f2)
    a = f1+f2;
    b = f1*f2;
end
If you put it in a script and call it with 1,2 and 3 output arguments:
% This works properly
a1 = fun(2,3)
a1 =
     5
% This also works
[a2, b2] = fun(2,3)
a2 =
     5
b2 =
     6
% This will give an error:
[a3, b3, c3] = fun(2,3)
Error using test>fun
Too many output arguments.
Error in test (line 8)
[a3, b3, c3] = fun(2,3)
Best regards
Stephan
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