For-loop error: Unable to perform assignment because the left and right sides have a different number of elements

I am currently trying to calculate the different processen in a combustion engine. For that I so calculated the change of volume, pressure and temperature. I'm now trying to calculate the heatflow.

Vphi,pphi and Tphi are all 1x7201 doubles.

Using the function gives me the error "Unable to perform assignment because the left and right sides have a different number of elements." in the line "warmth(i) = warmth(i-1) + dQ;". After a lot of troubleshooting I can't get it to work as a function. If I use it as a normal script it works without a problem for some reason. I would really like to use it as a function though.

Any help is highly appreciated.

function warmth = Warmth(Vphi, pphi, Tphi)

    global dk rs s n
    
    c_m = (s * n)/ 30;
    warmth = zeros(1,rs+1);
    dQ = 0;
        
    for i = 2:length(Vphi)
        
        alpha = dk^(-0.22) * 0.013 * pphi(i)^0.8 * Tphi(i) * 6.18 * c_m;
        A = Vphi(i)/(dk/2);
        dQ = alpha * A * (Tphi(i)-Tphi(i-1));
        
        warmth(i) = warmth(i-1) + dQ;
        
    end
end

[Matt J]

This works fine

global dk rs s n

[Vphi, pphi, Tphi]=deal(rand(1,7201));
[dk s n]=deal(1);
rs=10;

warmth_output = Warmth(Vphi, pphi, Tphi)

function warmth = Warmth(Vphi, pphi, Tphi)
    global dk rs s n
    
    c_m = (s * n)/ 30;
    warmth = zeros(1,rs+1);
    dQ = 0;
        
    for i = 2:length(Vphi)
        
        alpha = dk^(-0.22) * 0.013 * pphi(i)^0.8 * Tphi(i) * 6.18 * c_m;
        A = Vphi(i)/(dk/2);
        dQ = alpha * A * (Tphi(i)-Tphi(i-1));
        
        warmth(i) = warmth(i-1) + dQ;
        
    end
end

[Catalytic]

GLOBALS ?!?!?!??! Surely you must be joking.