what to do when array indicies exceed for , FOR loop comparision for below , trying to plot density of atmosphere, how to do the comparison ?

h(1) = 0;
T(1) = 273.15;
p(1) = 101.2;


for t = 1:328084
    
    if h(t)<[11000]
        T(t+1) = 15.04 - 0.00649.*h(t);
        p(t+1) = 101.29 .*((T(t) + 273.15) /288.08).^5.256;
    elseif [11000]> h(t) && h(t)<=[25000]
        T(t) = -56.46;
        p(t+1) = 22.65.*e^(1.73-0.000157.*h(t));
    elseif h(t)>[25000]
        T(t) = -131.21+0.00299.*h(t);
        p(t+1) = 2.488 .* ((T(t) + 273.15)/216.6).^-11.388;
        
    end
    
    rho_h(t) = p(t) ./(0.2869 * (T(t) + 273.15))   
    
    
end

figure(1)
plot(T,h)
grid on 
legend on

figure(2)
plot(rho_h, h)
grid on
legend on

Answer 1

[Walter Roberson]

h(1) = 0;

That is the only place you assign to h

    if h(t)<[11000]

but you need h to be 328084 elements by the end of the loop.

[SL]

it still doesnot work

[Walter Roberson]

What values do you assign to the remaining elements of h ?

[SL]

nothing I am varying h from 0 to 300000 ft , its height in feet, with the height I am calculating the density and temperature and pressure

[Walter Roberson]

h = linspace(0, 300000, 328084);

??

Or

h = 1 : 328084;

??

[SL]

still the error remains.

[Walter Roberson]

N = 328084;


h = 0:N-1;
T(1) = 273.15;
p(1) = 101.2;


for t = 1:N-1
    
    if h(t) <= 11000
        T(t+1) = 15.04 - 0.00649.*h(t);
        p(t+1) = 101.29 .*((T(t+1) + 273.15) /288.08).^5.256;
    elseif 11000 < h(t) && h(t) <= 25000
        T(t+1) = -56.46;
        p(t+1) = 22.65.*exp(1.73-0.000157.*h(t));
    else
        T(t+1) = -131.21+0.00299.*h(t);
        p(t+1) = 2.488 .* ((T(t+1) + 273.15)/216.6).^-11.388;
    end
    
    rho_h(t+1) = p(t+1) ./(0.2869 * (T(t+1) + 273.15));   
    
end

figure(1)
whos

  Name       Size                  Bytes  Class     Attributes

  N          1x1                       8  double              
  T          1x328084            2624672  double              
  h          1x328084            2624672  double              
  p          1x328084            2624672  double              
  rho_h      1x328084            2624672  double              
  t          1x1                       8  double              

plot(T,h)
grid on 
legend on

figure(2)
plot(rho_h, h)
grid on
legend on

[SL]

perfect thank you very much highly appreciate it

[Walter Roberson]

please recheck rho_h(1) which is not assigned a value.