call different matlab function in for loop (SIMULINK)

Dear community,

I'm having trouble getting a function to work, that calls a different beta function depending on the interval.

The getBeta_l function is created in a Matlab script, and has a suffix depending of the specific curvenumber.

How do I call the function and link it to my simulink variable s (curvelength)

manually it would look like this:

if  (0 <= s)&& (s<= R_kpi/2)

    beta = getBeta_1(s);

elseif (R_kpi/2 < s)&& (s<= R_k3pi/2)

       beta = getBeta_2(s);
elseif
.
.
.
.

now I'm trying to do this in a for loop, but I can't figure out, how to implement it properly...

if  (0 <= s)&& (s<= R_kpi/2)
    beta = getBeta_1(s);
else
     for q = 2:nuc %nuc = number of curves

        if (R_k(2q-3)pi/2 < s)&& (s<= R_kpi(2*q-1)/2) %Interval
            filename=['getBeta_l',num2str(q)]; %get function
            beta=filename(s); %call function (s)

        end
     end
end

Thanks for your help,

Johannes

Answer 1

[Udara De Silva]

Hi Johannes,

You can use Matlab 'run' command to do this as shown below:

if  (0 <= s)&& (s<= R_kpi/2)
    beta = getBeta_1(s);
else
     for q = 2:nuc %nuc = number of curves
        if (R_k(2q-3)pi/2 < s)&& (s<= R_kpi(2*q-1)/2) %Interval
            filename=['getBeta_',num2str(q)]; %get function
            run([filename, '(', num2str(s), ')']); % run function
            beta=ans; % assign ans to output variable
        end
     end
end

Best Regards,

Udara

[Johannes Wieser]

Thanks for your answer,

sadly num2str(q) doesn't work because num2str only supports a constant.

I've tried sprintf, but that requires a constant aswell.

Any suggestions on that?

[Udara De Silva]

Hi Johannes,

I'm not sure what you meant by num2str only supports a constant. I have tried calling num2str in a for loop and it works fine. Also, I tried run([filename,'(',num2str(q),')']); which works for me. May be you can share the exact error message you are getting.

Regards,

Udara

[Johannes Wieser]

Thanks for your help.

I think I wasn't explaining myself very well. I'm running this loop inside a Simulink MatLab function.

function beta = fcn(s,R_k, nuc)

if  (0 <= s)&& (s<= R_k*pi/2)
    beta = getBeta_1(s);
else
     for q = 2:nuc %nuc = number of curves
        if ((R_k*(2*q-3)*pi/2) < s)&& (s<= (R_k*pi*(2*q-1)/2)) %Interval
           filename=['getBeta_',num2str(q)]; %get function
           run([filename, '(', num2str(s), ')']); % run function
           beta=ans; % assign ans to output variable
        end
     end
end

This is the Error I am getting:

Best regards

Johannes

[Udara De Silva]

It seems that the error is thrown by Matlab Coder. So I assume although 'run' works in matlab it may not work in simulink. Can you try 'feval' instead of 'run'?

[Johannes Wieser]

It already fails before it gets to that line.

Answer 2

[Walter Roberson]

discretize() to get an index number. Use it to index a cell array of function handles, and execute the resulting handle. No loops needed, and no if statements other than checking to be sure the input is within the bounds of discretization.

[Johannes Wieser]

Thank you for your answer! I've looked through the documentation for discretize, but an an not sure how to implement it in my usecase.

I'm still very new to Matlab and programming.

It would be great if you could give me an example on how to use it in my usecase.

Thanks for your help!

Best regards

Johannes

[Walter Roberson]

Each time your q increases by 1, you move a "window" of width R_k further right and test to see if s is inside that window.

You could instead use

floor((s - SomeOffset)/Rk)

to directly calculate the appropriate q value. Discretization not needed.

You would have initialized

BH = {@getBeta_1, @getBeta_2, @getBeta_3 ... }

but first you would have put in an

assert(nuc <= SOME_LIMIT)

and then when you construct H, it will be either SOME_LIMIT or SOME_LIMIT+1 or SOME_LIMIT+2 entries (depending how you want to handle the boundary conditions on the two sides.) This assert() enforces that the index that gets used is no more than the maximum you configured for.

Once you have the index,

f = BH{q};
beta = f(appropriate_parameters);

Use real functions, not scripts for this purpose; Simulink cannot generate code for scripts.