for loop for multiple functions and output

Good Morning All,

Probably a silly question for most programmers but I am trying to create a loop that will run through two matlab functions.

I have two functions, boreprofile and fcoeffs_fft that I need to run for an iteration of n.

The two functions have the following input/output:

[profile, angles]=boreprofile(dn,CenterCoor,ImportDisp,ImportCoor);
[a0,ak,bk]=fcoeffs_fft(profile,angles,5);

Normally when I run the script I have to manually enter dn...for example:

[profile1, angles1]=boreprofile(1,CenterCoor,ImportDisp,ImportCoor);
[a01,ak1,bk1]=fcoeffs_fft(profile1,angles1,5);
Ak1=sqrt(ak1^2+bk1^2);
...
[profile2, angles2]=boreprofile(2,CenterCoor,ImportDisp,ImportCoor);
[a02,ak2,bk2]=fcoeffs_fft(profile2,angles2,5);
Ak2=sqrt(ak2^2+bk2^2);
...

I tried to make the for loop as follows but its producing the error "In an assignment A(I) = B, the number of elements in B and I must be the same." So I am assuming its not saving the variables the way I have envisioned.

for i=1:n
%Calculating profiles
[profile(i), angles(i)]=boreprofile(i,CenterCoor,ImportDisp,ImportCoor);
%Using f-coeffs_fft function to obtain fourier coefficients
[a0(i),ak(i),bk(i)]=fcoeffs_fft(profile(i),angles(i),5);
%Amplitude of distortion (Fourier Coefficients)
Ak(i)=sqrt(ak(i).^2 + bk(i).^2)*1000; 
end

Thanks!!!

[dpb]

What are output dimensions? Are they consistent for each run?

The basic answer is you need to encapsulate the various outputs in a cell array; the reference profile(i), etc., is to a single element of an array and so the total output of the function for that variable won't fit in a single element.

Look at

doc arrayfun

for one way

[Melissa]

Oh that makes sense to why that error is happening. I will look at the document and read through. To answer your question for the consistency of the output they will be for a given run but not necessarily every time. For example for one complete loop it may be 72x1 for the profile and angles where if I import anotehr round of data it may be 84x1 for profile and angles another time.

[Melissa]

Changed it and removed the indexing in the profile, angles, ak and bk. The code works but now overwrites every time. So another issue which I will google to attempt to find the solution that way.

for i=1:n
%Calculating profiles
[profile, angles]=boreprofile(i,CenterCoor,ImportDisp,ImportCoor);
%Using f-coeffs_fft function to obtain fourier coefficients
[a0,ak,bk]=fcoeffs_fft(profile,angles,5);
%Amplitude of distortion (Fourier Coefficients)
Ak=sqrt(ak.^2 + bk.^2)*1000; 
end

Answer 1

[Star Strider]

The outputs profile(i) angles(i) appear to be vectors, since you’re taking the fft (or inverse fft) of them.

If they’re in a row vector, name them as angles(i,:), if a column vector angles(:,i). The same for the results of fcoeffs_fft, if they’re vectors as well.

BTW, it’s best not to use ‘i’ and ‘j’ as index references, since MATLAB uses them as its imaginary operators. Using them as index references could create confusion.

[Melissa]

Thanks Star Strider. I will change the i and j to another variable name and after dpb said something similar above I realized that was the error. I changed my indexing and now I cant figure out how to store Ak since only the last iteration is being stored. I even used what I believe is pre-allocation and set Ak=zeros(n,5) before the loop. Any suggestions?

Ak=zeros(n,5);
for i=1:n
[profile, angles]=boreprofile(i,CenterCoor,ImportDisp,ImportCoor);
%Using f-coeffs_fft function to obtain fourier coefficients
[a0,ak,bk]=fcoeffs_fft(profile,angles,5);
%Amplitude of distortion (Fourier Coefficients)
Ak=sqrt(ak.^2 + bk.^2)*1000;
end

[Star Strider]

You need to index Ak and any others you want to store to keep all the interim values. How you do that depends on the size of Ak.

If it’s a scalar, just refer to it as Ak(index).

If it’s an array and doesn’t change size between loop iterations, use the indexing scheme I suggested for angles in my Answer.

If your variables are different sizes between loops, you may have to use a cell array. Cell arrays complicate things slightly, but are extremely useful.

[Melissa]

It worked!! Thanks you very much for all of your helpful advice :D

[Star Strider]

My pleasure!

Answer 2

[Aravindhan Anbarasu]

w=4;
c=3*10^5;
pt=10*log10(w/0.001);
d=0.5:0.1:5;
f=[830*10^6, 1880*10^6, 5.5*10^9];
for f=1:3
    pr=pt-21.98+20.*log10(c/f)-20.*log10(d);
     plot(log10(d),pr)
     hold on;
     grid on;

end

My y axis is different if I run this code if i use for loop and if i'm not using for loops the answer varies .

w=4;
c=3*10^5;
pt=10*log10(w/0.001);
d=0.5:0.1:5;
f=830*10^6
pr=pt-21.98+20.*log10(c/f)-20.*log10(d);
plot(log10(d),pr)
hold on;
f1=1880*10^6
pr1=pt-21.98+20.*log10(c/f1)-20.*log10(d);
plot(log10(d),pr1)
hold on
f2=5.5*10^9;
pr2=pt-21.98+20.*log10(c/f2)-20.*log10(d);
plot(log10(d),pr2)