Getting index outta bounds error for line 38 cant find out why

Line 38 is in bold

clear; clc;

fo=fopen('table.txt','w');

fprintf(fo,'      z(km)        p(Pa)         T(K)     rho(kg/m^3)  \n');

fprintf(fo,'--------------------------------------------------------\n');

R=287.0;

z=0:1000:50000;

z_i=[0 11.0 20.0 32.0 47.0 51.0];

T_i=[288.15 216.65 216.65 228.65 270.65 270.65];

p_i=[101325 22632.05 5474.88 868.02 110.91 66.94];

lambda_i=[0.0065 .0000 -0.001 -0.0028 0.0000];

g_i=[9.810 9.776 9.749 9.712 9.666 9.654];

type=[1 2];

for n = 1:length(z)

if z(n)>=z_i(1)&& z(n)<z_i(2)
z1(n)=z_i(1); p1(n)=p_i(1); T1(n)=T_i(1); lambda1(n)=lambda_i(1); 
g1(n)=g_i(1); type1=type(1);

elseif z(n)>=z_i(2)&& z(n)<z_i(3)
z1(n)=z_i(2); p1(n)=p_i(2); T1(n)=T_i(2);lambda1(n)=lambda_i(2);
g1(n)=g_i(2); type1=type(2);

elseif z(n)>=z_i(3)&& z(n)<z_i(4)
z1(n)=z_i(3);p1(n)=p_i(3);T1(n)=T_i(3);lambda1(n)=lambda_i(3);
g1(n)=g_i(3);type1=type(1);

elseif z(n)>=z_i(4)&& z(n)<z_i(5)
z1(n)=z_i(4); p1(n)=p_i(4); T1(n)=T_i(4); lambda1(n)=lambda_i(4);
g1(n)=g_i(4); type1=type(2);

elseif z(n)>=z_i(5)&& z(n)<z_i(6)
z1(n)=z_i(5); p1(n)=p_i(5); T1(n)=T_i(5); lambda1(n)=lambda_i(5);
g1(n)=g_i(5); type1=type(2);

end

if type1== type(1)

*p(n)=p1(n)*(1-(lambda1(n)*(z(n)-z1(n))/T1(n))).^(g1(n)/(lambda1(n)*R));*

T(n)=T1(n)-lambda1(n)*(z(n)-z1(n));

rho(n)=p1(n)/(R*T1(n));

end

if type1== type(2)

p(n)=p1(n)*exp(-1*g1(n)*(z(n)-z1(n))*(1/R)*(1/T1(n)));

T(n)=T1(n);

rho(n)=p1(n)/(R*T1(n));

end

end

fprintf(fo,'     %10.0i      %10.5e      %7.2f     %10.5e  \n',z,p,T,rho);

fclose(fo);

plot(T,z,p,z,rho,z);

Error Message is Attempted to access p1(2); index out of bounds because numel(p1)=1.

Error in Project_2 (line 38) p(n)=p1(n)*(1-(lambda1(n)*(z(n)-z1(n))/T1(n))).^(g1(n)/(lambda1(n)*R));

[Muthu Annamalai]

Can you please use the '{} Code' button to format your code?

My best effort leads me to,

    clear; clc;

    fo=fopen('table.txt','w');

    fprintf(fo,' z(km) p(Pa) T(K) rho(kg/m^3) \n');

    fprintf(fo,'--------------------------------------------------------\n');

    R=287.0;

    z=0:1000:50000;

    z_i=[0 11.0 20.0 32.0 47.0 51.0];

    T_i=[288.15 216.65 216.65 228.65 270.65 270.65];

    p_i=[101325 22632.05 5474.88 868.02 110.91 66.94];

    lambda_i=[0.0065 .0000 -0.001 -0.0028 0.0000];

    g_i=[9.810 9.776 9.749 9.712 9.666 9.654];

    type=[1 2];

    for n = 1:length(z)

    if z(n)>=z_i(1)&& z(n)<z_i(2) z1(n)=z_i(1); p1(n)=p_i(1); T1(n)=T_i(1); lambda1(n)=lambda_i(1); g1(n)=g_i(1); type1=type(1);

    elseif z(n)>=z_i(2)&& z(n)<z_i(3) z1(n)=z_i(2); p1(n)=p_i(2); T1(n)=T_i(2);lambda1(n)=lambda_i(2); g1(n)=g_i(2); type1=type(2);

    elseif z(n)>=z_i(3)&& z(n)<z_i(4) z1(n)=z_i(3);p1(n)=p_i(3);T1(n)=T_i(3);lambda1(n)=lambda_i(3); g1(n)=g_i(3);type1=type(1);

    elseif z(n)>=z_i(4)&& z(n)<z_i(5) z1(n)=z_i(4); p1(n)=p_i(4); T1(n)=T_i(4); lambda1(n)=lambda_i(4); g1(n)=g_i(4); type1=type(2);

    elseif z(n)>=z_i(5)&& z(n)<z_i(6) z1(n)=z_i(5); p1(n)=p_i(5); T1(n)=T_i(5); lambda1(n)=lambda_i(5); g1(n)=g_i(5); type1=type(2);

    end

    if type1== type(1)

    p(n)=p1(n)*(1-(lambda1(n)*(z(n)-z1(n))/T1(n))).^(g1(n)/(lambda1(n)*R));

    T(n)=T1(n)-lambda1(n)*(z(n)-z1(n));

    rho(n)=p1(n)/(R*T1(n));

    end

    if type1== type(2)

    p(n)=p1(n)*exp(-1*g1(n)*(z(n)-z1(n))*(1/R)*(1/T1(n)));

    T(n)=T1(n);

    rho(n)=p1(n)/(R*T1(n));

    end

    end

    fprintf(fo,' %10.0i %10.5e %7.2f %10.5e \n',z,p,T,rho);

    fclose(fo);

    plot(T,z,p,z,rho,z);

Answer 1

[Geoff Hayes]

Brad - if you step through the code, using the debugger, you will notice that on the first iteration of the for loop, n==1, the if condition evaluates to true and all arrays are updated with the first element. On the second iteration of the for loop, n==2, no condition for the if or any elseif evaluates to true and so none of the arrays are updated with the second element. And so at line 32 (or 33) the code tries to access p1(2) in an array that only has 1 element.

Either you need to review your conditions, or add an else statement that sets some default values for your five arrays.

EDIT

Note how your z array is initialized as

 z = 0:1000:50000

and so is composed of 0,1000,2000,.. i.e. multiples of 1000. But your z_i array is

 z_i=[0 11.0 20.0 32.0 47.0 51.0];

So it is impossible for any value in z except for 0 (the first one) to satisfy any of the conditions which is using z_i as interval bounds for the z data.

[Brad]

Geoff thanks for your help that fixed it right away only problem i am having now is my table isn't computing the proper numbers the z is going up in the wrong interval here is the updated program that runs with no errors now i was wondering if you could help with that

clear; clc;
fo=fopen('table.txt','w');
fprintf(fo,'      z(km)        p(Pa)         T(K)     rho(kg/m^3)  \n');
fprintf(fo,'--------------------------------------------------------\n');
R=287.0;
z=0:1000:50000;
z_i=[0 11000 20000 32000 47000 51000];
T_i=[288.15 216.65 216.65 228.65 270.65 270.65];
p_i=[101325 22632.05 5474.88 868.02 110.91 66.94];
lambda_i=[0.0065 .0000 -0.001 -0.0028 0.0000];
g_i=[9.810 9.776 9.749 9.712 9.666 9.654];
type=[1 2];
for n = 1:length(z)
    if z(n)>=z_i(1)&& z(n)<z_i(2)
        z1(n)=z_i(1); p1(n)=p_i(1); T1(n)=T_i(1); lambda1(n)=lambda_i(1); 
        g1(n)=g_i(1); type1=type(1);
    elseif z(n)>=z_i(2)&& z(n)<z_i(3)
        z1(n)=z_i(2); p1(n)=p_i(2); T1(n)=T_i(2);lambda1(n)=lambda_i(2);
        g1(n)=g_i(2); type1=type(2);
    elseif z(n)>=z_i(3)&& z(n)<z_i(4)
        z1(n)=z_i(3);p1(n)=p_i(3);T1(n)=T_i(3);lambda1(n)=lambda_i(3);
        g1(n)=g_i(3);type1=type(1);
    elseif z(n)>=z_i(4)&& z(n)<z_i(5)
        z1(n)=z_i(4); p1(n)=p_i(4); T1(n)=T_i(4); lambda1(n)=lambda_i(4);
        g1(n)=g_i(4); type1=type(2);
    elseif z(n)>=z_i(5)&& z(n)<z_i(6)
        z1(n)=z_i(5); p1(n)=p_i(5); T1(n)=T_i(5); lambda1(n)=lambda_i(5);
        g1(n)=g_i(5); type1=type(2);
    end
    if type1== type(1)
        p(n)=p1(n)*(1-(lambda1(n)*(z(n)-z1(n))/T1(n))).^(g1(n)/(lambda1(n)*R));
        T(n)=T1(n)-lambda1(n)*(z(n)-z1(n));
        rho(n)=p1(n)/(R*T1(n));
    end
    if type1== type(2)
        p(n)=p1(n)*exp(-1*g1(n)*(z(n)-z1(n))*(1/R)*(1/T1(n)));
        T(n)=T1(n);
        rho(n)=p1(n)/(R*T1(n));
    end
end
fprintf(fo,'     %10.0i      %10.5e      %7.2f     %10.5e  \n',z,p,T,rho);
fclose(fo);
figure
plot(T,z)
title('temperature vs altitude')
xlabel('temperature')
ylabel('altitude')
figure
plot(p,z)
title('pressure vs altitude')
xlabel('pressure')
ylabel('altitude')
figure
plot(rho,z)
title('air density vs altitude')
xlabel('air density')
ylabel('altitude')

The attached pdf is the table i'm getting from the program now it's suppose to have z start at 0 go to 50000 in intervals of 1000

[Geoff Hayes]

Brad - according to the documentation for fprintf,

fprintf(fileID,formatSpec,A1,...,An) applies the formatSpec to all elements of arrays A1,...An in column order, and writes the data to a text file.

So if you want to write out four columns of data, then your input to fprintf should be a 4xm array

 fprintf(fo,'     %10.0i      %10.5e      %7.2f     %10.5e  \n',[z;p;T;rho]);

Try replacing your fprintf with the above and see what happens.

[Brad]

Worked perfectly thank you for all your help

[Geoff Hayes]

Glad it worked out!