Why won't the arrays I make work in the functions I created where I need to find pressure?

I need to find pressure but the arrays won't plug into my functions as I keep getting D = 0. Is there any ways to fix this? Thanks!

%% Calculating Pressure

% Gives 201 values
for x = 0:30000:6000000


    % calculates the dome height at every x value
    D = calc_dome_height(x);

    % for every x value get all the verticle locationso
    for z = 0 : 50 : 10000
        
        % calculates the reference temperature
        ref_T = calc_ref_temp(z,D);

        % calculates the reference pressure
        ref_P = calc_ref_pressure(z,D);


        % calculates the pressure
        p = calc_pressure(ref_P,ref_T,z,D);
        
    end

end

Unrecognized function or variable 'calc_warm_temp'.

Error in solution>calc_pressure (line 83)
temp_w = calc_warm_temp(z);

function [D] = calc_dome_height(x)

    if x < 1000000
        D = 0;

    elseif (1000000 <= x) && (x <= 5000000)

        D = 5000 .* sin((pi/4000000).*(x - 1000000));
      
    elseif x >= 5000000

        D = 0;


    end
end
function [temp_c] = calc_cold_temp(z, D)

temp_c = 300 - (0.004 - -0.007) .* D - -0.007* z;

end
function [ref_T] = calc_ref_temp(z, D)

if z <= D
    ref_T = 300;

elseif z > D
    
    ref_T = 300 - (0.004 .* D);
end

end

function [ref_P] = calc_ref_pressure(z,D)

if z <= D

    ref_P = 1000;

elseif z > D

    temp_c = calc_cold_temp(D,D);

    ref_P = 1000* ((temp_c/300)^(9.81/(287*-0.007)));

end

end
function [pressure] = calc_pressure(ref_P, ref_T, z, D)

if z <= D

    temp_c = calc_cold_temp(z,D);

    pressure = ref_P * ((temp_c / ref_T)^(9.81/(287 * -0.007)));
elseif z > D

    temp_w = calc_warm_temp(z);

    pressure = ref_P * ((temp_w / ref_T)^(9.81/(287* 0.004)));
end

end

[Walter Roberson]

We need the calc_warm_temp function to test with.

[Torsten]

@Matthew

What exactly do you mean ? As you can see, D is not always equal to 0.

iter = 0;
for x = 0:30000:6000000
    % calculates the dome height at every x value
    iter = iter + 1;
    D(iter) = calc_dome_height(x);
end
plot(1:iter,D)

function [D] = calc_dome_height(x)
if x < 1000000
    D = 0;
elseif (1000000 <= x) && (x <= 5000000)
    D = 5000 .* sin((pi/4000000).*(x - 1000000));
    
elseif x >= 5000000
    D = 0;
end
end

Answer 1

[Walter Roberson]

    D = calc_dome_height(x);

That overwrites all of D for every iteration of the for loop, so at the end of the for loop, D is going to be whatever it was calculated to be for the last iteration. Which is going to e 0 because of the

    elseif x >= 5000000
        D = 0;

You are not recording each D as it is produced.

[Matthew]

What could I do to make sure it does capture each iteration of D? Make that D a different variable name like D1? Thanks

[Walter Roberson]

I suggest you read https://www.mathworks.com/matlabcentral/answers/2032249-to-plot-1d-temperature-distribution-plot-versus-lenght-of-the-channel-of-the-fin#comment_2926184 with example code in the same thread.

Answer 2

[Matthew]

Here's the code with everything. I want to go through each element of the x array and z array in order to get pressure at each value. Is there anyway to do that so D doesn't always equal zero? Thanks.

% Gives 201 values


    % calculates the dome height at every x value
     for x = 0:30000:6e6;
    D = calc_dome_height(x);
     for z = 0:50:10000;
        ref_T2 = calc_ref_temp(z,D);

        % calculates the reference pressure
        ref_P2 = calc_ref_pressure(z,D);


        % calculates the pressure
        p1 = calc_pressure(ref_P2,ref_T2,z,D);
     end
     end
function D = calc_dome_height(x)

    if all(x < 1000000)
        D = 0;

    elseif (1000000 <= x) && (x <= 5000000)

        D = 5000 .* sin((pi/4000000).*(x - 1000000));
      
    elseif all(x > 5000000)

        D = 0;
    end
end
% Reference Temperature Calculation
function ref_T = calc_ref_temp(z, D)

if z <= D
    ref_T = 300;

elseif z > D
    ref_T = 300 - (0.004 .* D);
end
end

function temp_c = calc_cold_temp(z, D)

temp_c = 300 - (0.004 - -0.007) .* D - -0.007* z;

end

% Warm Teperature Calculation
function [temp_w] = calc_warm_temp(z)

temp_w = 300 - 0.004 * z;

end

% Reference Pressure Calculation 
function [ref_P] = calc_ref_pressure(z,D)

if z <= D

    ref_P = 1000;

elseif z > D

    temp_c = calc_cold_temp(D,D);

    ref_P = 1000* ((temp_c/300)^(9.81/(287*-0.007)));

end

end

% Pressure Calculation
function [pressure] = calc_pressure(ref_P, ref_T, z, D)

if z <= D

    temp_c = calc_cold_temp(z,D);

    pressure = ref_P * ((temp_c / ref_T)^(9.81/(287 * -0.007)));
elseif z > D

    temp_w = calc_warm_temp(z);

    pressure = ref_P * ((temp_w / ref_T)^(9.81/(287* 0.004)));
end

end