How to skip some values in for loop ?

Dear All,

I am triyng to fill the I_dd array using the array called B_matrix. I initialize the first values of the I_dd array as 1 and then I use this value incrementally to fill following elements of the I_dd . Some elements of my B_matrix array are equal to zero and I want to just skip them. My B_matrix array is:

B(:,:,1) = [3     1     1
            1     0     0
            1     0     1]
B(:,:,2) = [0     0     0
            0     0     1
            0     1     2]
B(:,:,3) = [0     0     0
            0     0     0
            0     0     0]

My code is shown below:

I_dd = zeros(3,3,3);
for k = 1:3
    for i = 1:3
        for j = 1:3
            if i==1 && j==1 && k == 1
                I_dd(i,j,k) = 1;
            elseif j>1
                I_dd(i,j,k) = I_dd(i,j-1,k) + B_matrix(i,j-1,k);
            elseif i>1
                I_dd(i,j,k) = I_dd(i-1,3,k) + B_matrix(i-1,3,k);
            else
                I_dd(i,j,k) = I_dd(3,3,k-1) + B_matrix(3,3,k-1);
            end
        end
    end
end

The resulting I_dd array is shown below:

I_dd(:,:,1) = [1     4     5
               6     7     7
               7     8     8]
I_dd(:,:,2) = [9     9     9
               9     9     9
               10     10     11]
I_dd(:,:,3) = [13     13     13
               13     13     13
               13     13     13]

However, the correct I_dd should be:

I_dd(:,:,1) = [1     4     5
               6     0     0
               7     0     8]
I_dd(:,:,2) = [0     0     0
               0     0     9
               0     10     11]
I_dd(:,:,3) = [0     0     0
               0     0     0
               0     0     0]

The problem is due to zeros in the B_matrix. I tried to use continue command but it did not work. ould you please help me about fixing this issue?

I am looking forward to hearing from you

[Stephen23]

@mustafa ozendi: remember to accept my answer (the one where you got that code from):

https://www.mathworks.com/matlabcentral/answers/438601-filling-an-array-with-recursive-function

You have taken my code and are using it, but have not accepted my answer where you got that code from. Accepting answers shows that you value the help of the volunteers who help you.

Answer 1

[Stephen23]

Just add this line after those loops:

I_dd(B==0) = 0

to get this:

I_dd(:,:,1) =
    1    4    5
    6    0    0
    7    0    8
I_dd(:,:,2) =
    0    0    0
    0    0    9
    0   10   11
I_dd(:,:,3) =
    0    0    0
    0    0    0
    0    0    0   

Note that it is not really possible to do this inside the loops (as you tried) because later loop iterations depend on the values calculated during earlier loop iterations, which means that it is simpler to calculate all values of all loop iterations. But that simple line of code I showed you will give you exactly what you requested, after the loops have finished.

[mustafa ozendi]

Thanks Stephan