Getting Error: Unrecognized Function or Variable

When calling my aircondition.m function in Task 2, I get this error for my "rho" variable (and presumably P and T). After separately testing the function itself, my variables are defined at the end of the function. Unsure why else I'd be getting this or how I can fix it?

function [rho,P,T] = aircondition(h)
    
    R = 287;                     %gas constant for air
    g = 9.8;                        %gravity
    
    if h>=0 && h<=11000          %calculations for troposphere
        P_init = 101325;
        T_init = 288.15;
        xi = -0.0065;        
        T = T_init+(xi*(h-0));
        P = P_init*((T/T_init)^((-g)/(xi*R)));
        rho = P/(R*T);        
    elseif h>11000 && h<=20000      %calculations for tropopause       
        P_init = 22659.44596;        
        T = 216.65;
        P = P_init*exp(((-g)/(R*T))*(h-11000));
        rho = P/(R*T);        
    elseif h>20000 && h<=32000      %calculations for stratosphere 1        
        P_init = 5487.79142;
        T_init = 216.65;
        xi = 0.0010;        
        T = T_init+(xi*(h-20000));
        P = P_init*((T/T_init)^((-g)/(xi*R)));
        rho = P/(R*T);        
    elseif h>32000 && h<=47000      %calculations for stratosphere 2
        P_init = 871.35791;
        T_init = 228.65;
        xi = 0.0028;        
        T = T_init+(xi*(h-32000));
        P = P_init*((T/T_init)^((-g)/(xi*R)));
        rho = P/(R*T);      
    end
    
end

%%Then, calling the function:

m = input('Enter hydrogen mass in kg') + 40;        %total balloon mass
delta_t = input('Enter time step in seconds');      %time step input

g = 9.8;                   %setting up needed constants
R_air = 287;
R_h2 = 4124;
T_s = 110.4;
T_ref = 288.15;
mew_ref = 1.789E-5;
weight = m*g;              %weight force

i = 1;                     %increment counter
h = 0;                  %initial altitude
w = 0;                  %initial upward velocity
V = 0;                  %initial velocity placeholder
t = 0;                  %initial time


    while h(i) < 32000 && V(i) < 5000
        
        [rho,P,T] = aircondition(h(i));    %calculate current air conditions
        V(i) = (m*R_h2*T)/P;                  %calculate current balloon volume
    
        B = rho*V(i)*g;                          %Bouyancy force
    
        mew = mew_ref*((T/T_ref)^1.5)*((T_ref+T_s)/(T+T_s));    %current mew
        Re = (rho*w(i)*2*R_air)/mew;                    %current Reynolds Num.
        Cd = (24/(1+Re))+(6/(1+sqrt(Re)))+0.1;          %current Cd coeff.
        D = (0.5)*rho*(w(i)^2)*pi*(R_air^2)*Cd;      %current Drag Force
    
        a = (B-D-weight)/m;             %current acceleration
    
        h(i+1) = h(i)+(w(i)*delta_t);     %update height
        w(i+1) = w(i)+(delta_t*a);        %update velocity
        V(i+1) = V(i);                  %placeholder
        i = i+1;
    
    end

[Sindar]

this doesn't seem like the issue here, but I'd add an else line with an informative error:

elseif h>32000 && h<=47000      %calculations for stratosphere 2
        P_init = 871.35791;
        T_init = 228.65;
        xi = 0.0028;        
        T = T_init+(xi*(h-32000));
        P = P_init*((T/T_init)^((-g)/(xi*R)));
        rho = P/(R*T);
else
    error('h=%g is greater than the limit of 47000',h)
end

Answer 1

[Walter Roberson]

If your balloon starts descending before it reaches 32000 units, then it will reach the ground, h < 0, which is a condition not defined in your aircondition() function.

g = 9.8;                   %setting up needed constants

That constant is in the unit meters per second^2

    elseif h>11000 && h<=20000      %calculations for tropopause       

when I look at wikipedia, it looks to me as if you might be using feet for those boundaries rather than meters ??