How to input signal to skip numbers and generate data?

I have a set of random 0s and 1s matrix A = [0 0 0 0 0 1 1 1 0 0 0 0 1 0 1 1 0 0 1 1 1 1 1 0 0 0 0]. I want to create a matrix B that has the same size as A that if i input an interval of say 'n', it skips n numbers, and if it lands on 1, it records 1 but if it lands on 0 it records 0. however, if it doesnt land on 1 for a long time and finally lands on a 1, it records a 1 even though it has skipped more than n numbers. How do I create this matrix B?

For example, n = 2, then matrix B = [0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 1 0 0 1 0 0 1 0 0 0 0 0]

Answer 1

[Mara]

A       = [0 0 0 0 0 1 1 1 0 0 0 0 1 0 1 1 0 0 1 1 1 1 1 0 0 0 0];
n       = 2;
B       = zeros (1,length(A));
count   = 0;

for i = 1:length(A)
    count = count + 1;
    if A(i) == 1 && count > n
        B(i) = 1;
        count = 0;
    end  
end

Does this help you?

[Leon Low]

Thank you so much Mera! You have saved me so much time...

Do you know how I can set it in a way where I can choose where to start the system?

For example, i want to start from the 7th one in matrix A. and n = 2

A = [0 0 0 0 0 1 1 1 0 0 0 0 1 0 1 1 0 0 1 1 1 1 1 0 0 0 0].

So, B = [0 0 0 0 0 1 1 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 0]

[Mara]

Hey Leon, glad I could help. If you know the position you want to start with, I think the easiest way might be to include another if statement. If i is taller than or equal to the start position 7, it starts skipping and before that it will just copy the elements of A one by one.

A       = [0 0 0 0 0 1 1 1 0 0 0 0 1 0 1 1 0 0 1 1 1 1 1 0 0 0 0];
n       = 2;
B       = zeros (1,length(A));
count   = n;    % the starting value of count needs to be changed if
                %  you want to be able to start skipping with a 1 right away
start   = 7;

for i = 1:length(A)
    if i >= start
        count = count + 1;
        if A(i) == 1 && count > n
            B(i)    = 1;
            count   = 0;
        end 
    else
        B(i) = A(i)
    end
end

or this way, make B a copy of A right at the beginning and then start looping from the starting position.

A       = [0 0 0 0 0 1 1 1 0 0 0 0 1 0 1 1 0 0 1 1 1 1 1 0 0 0 0];
n       = 2;
B       = A;
count   = n; % if you want to be able to start skipping with a 1 right away
start = 7;

for i = start:length(A)
        count = count + 1;
        if A(i) == 1 && count > n
            B(i)    = 1;
            count   = 0;
        else 
            B(i) = 0;
        end 
end

[Leon Low]

Thank you so much Mera! It works as usual :)

[Leon Low]

Hey Mera, how do I force the system matrix A to start from the first “1” it sees? When I try to put n=8, it does not start from the first “1”

[Mara]

there are many different ways to find the first nonzero position, one is the function find().

Citing the documentation:

k = find(X,n) returns the first n indices corresponding to the nonzero elements in X.

type "doc find" in the command window for more info.

Best,

Mara