How do I return multiple array values?

This is a code that calculates the curvature and moment capacity of the given pre-stressed concrete beam section. I try returning two values from the

function: curvature and the total_moment. However, there is only one output which is the first element of the returning array. The code is:

function [curvature, moment] = axis_matlab(ec_top)
    %curv = 0;
    %moment = 0;
    %ec_top = 0.001;
    h = 910;
    d = 795;
    ht = 180;
    b = 450;
    bw = 140;
    As = 1700;
    %fp = 1100;
    fcu = 50;
    Ec = 12680 + 460 * fcu;
    Es = 200 * 1e3;
    ec0 = 2 * fcu / Ec;
    %ecu = 0.0038;
    for c = 0:5e-3:h
        fs = Es * (c - d) * ec_top / c;
        Fs = fs * As * 1e-3;
        lis = linspace(0, c, c * 10);
        total_force = Fs;
        total_moment = Fs * (d - h / 2) * 1e-3 * -1;
        for i = 1:1:(length(lis) - 1)     
            if lis(i) <= ht && lis(i) >= h - ht
                b_i = b;
            else
                b_i = bw;
            end
            h_i = lis(i + 1) - lis(i);
            y_i = (h / 2) - lis(i) + (h_i / 2);
            e_i = c - lis(i) + (h_i / 2);
            ec_i = ec_top * (c - e_i) / c;
            fc_i = fcu * ((2 * ec_i / ec0) - (ec_i / ec0) ^ 2);
            Fc_i = fc_i * h_i * b_i * 1e-3;
            M_i = Fc_i * y_i * 1e-3;
            total_force = total_force + Fc_i;
            moment = total_moment + M_i; 
            curvature = ec_top / c;
        end
        if -1 < total_force && total_force < 1
            break;
        end
    end
end

"""

I ended up with this result:

>> axis_matlab

ans = 

 1.1270e-05

How do I get all return values from the function?

Additionally, I want to optimize this function as it iterates two many numbers to get the exact "c" value. Actually, the function was based on Python Language but I turned into Matlab document to get faster on running the code. As its known, there are different types for keeping the data (lists, tuples, sets and dicts.) in Python, to get the faster results, the list type must be adjusted properly. Is there any similar way to optimize the above function?

Answer 1

[Star Strider]

If you want both outputs, ask for them!

Call your function as:

[curvature, moment] = axis_matlab

If your function is working correctly, both values will be returned to your workspace.

‘Additionally, I want to optimize this function as it iterates two many numbers to get the exact "c" value.’

I have no idea what your function is doing. It may be as efficient as it can be. Some things just require iterating until the code arrives at the correct result.

[Said Bolluk]

Thank you for your help. This function iterates numbers starting from zero to find the neutral axis depth value "c". And this calculation repeats for each strain value: ec = 0 : 1e-10 : 0.0038. I know there lots of technical terms but the idea is to determine the behaviour of the beam section and the function iterates the value based on the force equilibrium. My second question was simply: How to make function easier for MATLAB to run by considering the huge amount of iteration?

[Star Strider]

As always, my pleasure.

It might be possible to use one of the optimization functions, however I have no idea what your function is doing, or what needs to be optimized. (Concrete beams are not an area of my expertise.) If you have a paper describing the functions and the objective of the calculations, it might be easier to understand. Your function runs fast on my computer, so I would just leave it as it is.

[Said Bolluk]

The above code is just a part of the main code that I attached in the post. I will try to explain the code "moment_curvature_matlab" briefly. When a section is loaded, moment causes forces to occur in couples: compression and tensile. Concrete material produces the compression while steel reinforcement produces tensile forces. The neutral axis is where the total_force is equal to zero (in code, it get closer to zero: if statement). To find the neutral axis, I separated the concrete material which is above the neutral axis (compression zone) as it is a more precise way. After finding neutral axis depth "c" for each strain value (ec = 0 : 0.0038), I calculate the curvature and moment values and, finally plot this kind of behaviour. There would be tons of iteration if its desired to have more consistent values. I wonder if there is any list-manipulation to make code run faster.

[Star Strider]

I do not understand what your code is doing. If you could provide symbolic expressions of the calculations you are doing, it might be possible to suggest an optimization function approach to it.