How to change the value of a variable each time a loop runs?

Hello, I am working with this code below:

D = cell(num_ds, 1);
    for k = 1 : num_ds
        D{k} = A{k,1}+DI-20*log(r)-alpha*r+deltaL-10.8;
    end

It is the outdoor sound propagation equation. This loop as it stands now produces the variable D that has 5 cells containing five 1x8 matrices representing decibel values. I need to be able to change the value of alpha for each cell, i.e. say the matrix contains the values 62,66,45,78,36,75,36,75 each one of these values needs to be computed with a different value of alpha. I am not sure how to get this to work to not only one matrix but all of them consistently.

I hope I explained this well enough!

The values of alpha that are needed to run through are 0.271, 0.579, 1.2, 3.27, 11, 36.2, 91.5 and 154

Answer 1

[James Tursa]

Do you want each result in a different cell? E.g.,

alpha = [0.271, 0.579, 1.2, 3.27, 11, 36.2, 91.5, 154];
D = cell(num_ds, numel(alpha));
for k = 1 : num_ds
    for m = 1 : numel(alpha)
        D{k,m} = A{k,1}+DI-20*log(r)-alpha(m)*r+deltaL-10.8; % fixed typo
    end
end

[Alison Alexsy]

Cell contents reference from a non-cell array object.

Error in Sound_Code (line 60) D{k,m} = A{k,1}+DI-20*log(r)-alpha{m}*r+deltaL-10.8;

[James Tursa]

Oops. Typo. Use alpha(m) instead of alpha{m}.

[Alison Alexsy]

Fixed it, it runs now however it produces a 5x8 matrix, is there anyway it can have the same format of the other variables I have where D has five different cells containing each individual matrix?

[James Tursa]

What is in the A{k,1}? A scalar, vector, or matrix? E.g., does each A{k,1} contain a 1x8 vector? What are the sizes of the other variables? If r is a scalar, it is not clear to me why your original code wouldn't work for you. If r is a vector, them maybe this does what you want:

D{k} = A{k,1}+DI-20*log(r)-alpha.*r+deltaL-10.8;

[Alison Alexsy]

A{1,1} - A{5,1} are 1x8 vectors

[Alison Alexsy]

Everything is a scalar except A and now alpha, using that code I got the error:

Error using - Matrix dimensions must agree.

Error in Sound_Code (line 60) D{k} = A{k,1}+DI-20*log(r)-alpha.*r+deltaL-10.8;

I changed alpha to

alpha = [0.271; 0.579; 1.2; 3.27; 11; 36.2; 91.5; 154];

and that fixed it, but now D has blank squares