Output argument "variable" (and maybe others) not assigned during call to "function".

I'm creating a program that models the flight path of a satellite in low earth orbit, where the changing densities is necessary to compute the drag forces. My function for calculating the drag forces is as follows:

function [ax,ay] = LEO_drag_acceleration(x,y,vx,vy,g)

C_d = 2.2;

h = y;

A = .3;

vel = sqrt(vx.^2 + vy.^2);

rho = LEO_density_range(h);

ax = -((rho*C_d*A)/2)*vel*vx;

ay = -g-((rho*C_d*A)/2)*vel*vy;

return

end

and the LEO_density_range function is as follows:

function rho = LEO_density_range(h)

 if h < 25000

     rho = 1.225;

 elseif h >= 25000 && h < 30000;

     rho = 3.899*10^-2;

 elseif h >= 30000 && h < 40000;

     rho = 1.744*10^-2;

 elseif h >= 40000 && h < 50000;

     rho = 3.972*10^-3;

 elseif h >= 50000 && h < 60000;

     rho = 1.057*10^-3;

 elseif h >= 60000 && h < 70000;

     rho = 3.206*10^-4;

 elseif h >= 70000 && h < 80000;

     rho = 8.770*10^-5;

 elseif h >= 80000 && h < 90000;

     rho = 1.905*10^-5;

 elseif h >= 90000 && h < 100000;

     rho = 3.396*10^-6;

 elseif h >= 100000 && h < 110000;

     rho = 5.297*10^-7;

 elseif h >= 110000 && h < 120000;

     rho = 9.661*10^-8;

 elseif h >= 120000 && h < 130000;

     rho = 2.438*10^-8;

 elseif h >= 130000 && h < 140000;

     rho = 8.484*10^-9;

 elseif h >= 140000 && h < 150000;

     rho = 3.845*10^-9;

 elseif h >= 150000 && h < 180000;

     rho = 2.070*10^-9;

 elseif h >= 180000 && h < 200000;

     rho = 5.465*10^-10;

 elseif h >= 200000 && h < 250000;

     rho = 2.789*10^-10;

 elseif h >= 250000 && h < 300000;

     rho =  7.248*10^-11;

 return

 end

Any ideas on how to solve this issue?

This is the actual error message: "Output argument "rho" (and maybe others) not assigned during call to "LEO_density_range"."

Answer 1

[Sriram Tadavarty]

Hi blackg2,

Based on the error message and the code provided, it is possible that the when the value of h is greater than or equal to 300000, the function doesn't assign rho, since there is no condition in the code which assign rho for those values. I think the function LEO_density_range is getting called with h greater than 300e3 and due to which the error is observed.

You can try to assign a default value in case any of the condition is not satisfied and also, the return call in the last elseif statement is not required.

Sample code:

if cond1
elseif cond2
else
    % Default case
    rho = 5e-12; % some value
end

Adding the above else case would avoid the error.

Hope this helps.

Regards,

Sriram