Finding Indices of Zeroes Following Non-Zero Elements in MATLAB

Hello everyone,

I am working on a MATLAB project where I have a numeric array, which is a series of numbers including zeroes and non-zero numbers. An example of the sequence is as follows: seq = [0,0,0,0,0,0 (find index),1,3,5,2,4,6,7,8,3,0 (find index),0,0,0 (find index),4,1,10,22,11,22,44,44,12,0 (find index),0,0,0]; In this sequence, I am trying to find the indices of zeroes that come immediately after a non-zero number. In the provided sequence, the output should be [6, 16, 19, 29].

Can you help me to write the code? Thank you

Answer 1

[Chunru]

x = [0,0,0,0,0,0,1,3,5,2,4,6,7,8,3,0,0,0,0,4,1,10,22,11,22,44,44,12,0,0,0,0];
x1 = x>0  % clipped x

x1 = 1×32 logical array
   0   0   0   0   0   0   1   1   1   1   1   1   1   1   1   0   0   0   0   1   1   1   1   1   1   1   1   1   0   0   0   0

i1 = find(diff(x1)>0)

i1 = 1×2

6 19

i2 = find(diff(x1)<0)+1

i2 = 1×2

16 29

i = sort([i1 i2])

i = 1×4

6 16 19 29

Answer 2

[Harshavardhan Putta]

Hi,

I understand that you are working on a MATLAB project where you have a numeric array consisting of both zero and non-zero numbers. The specific sequence you provided as an example contains various elements, including zeros. Your goal is to find the indices of zeroes that immediately follow a non-zero number in the sequence.

To accomplish this, you plan to iterate through the array and examine each element. If you encounter a non-zero number, you will check the subsequent element to determine if it is zero. If it is, you will record the index of that zero in a separate list.

% Given sequence
seq = [0,0,0,0,0,0,1,3,5,2,4,6,7,8,3,0,0,0,4,1,10,22,11,22,44,44,12,0,0,0];

% Find indices of zeroes after a non-zero number
indices = [];
for i = 1:length(seq)-1
    if seq(i) ~= 0 && seq(i+1) == 0
        indices = [indices, i+1];
    end
end

disp(indices);

I hope it helps!

Answer 3

[Anamika]

Here's an example code that finds the indices of zeroes that finds the indices of zeroes that come immediately after a non-zero number in a given sequence:

seq = [0,0,0,0,0,0,1,3,5,2,4,6,7,8,3,0,0,0,4,1,10,22,11,22,44,44,12,0,0,0];

%indices of non-zero numbers

nonZeroIndices = find(seq ~= 0);

%indices of zeroes that come immediately after a non-zero number

zeroIndices = nonZeroIndices(find(diff(nonZeroIndices) == 1)) + 1;

disp(zeroIndices);

What this code is evaluating?

This code first finds the indices of non-zero numbers in the sequence using the find function, to find the difference between consecutive non-zero indices can use diff function, by comparing these differences to 1 can identify the indices of zeroes that come immediately after a non-zero number after this finally, the code adds 1 to these indices to obtain the desired output.

The output of the above code will be: 6 16 19 29

Answer 4

[Bruno Luong]

seq = [0,0,0,0,0,0,1,3,5,2,4,6,7,8,3,0,0,0,0,4,1,10,22,11,22,44,44,12,0,0,0,0]

seq = 1×32

0 0 0 0 0 0 1 3 5 2 4 6 7 8 3 0 0 0 0 4 1 10 22 11 22 44 44 12 0 0

b = seq ~= 0;
union(findstr(b, [0 1]), findstr(b,  [1 0])+1)

ans = 1×4

6 16 19 29

[Bruno Luong]

A variation

seq = [0,0,0,0,0,0,1,3,5,2,4,6,7,8,3,0,0,0,0,4,1,10,22,11,22,44,44,12,0,0,0,0]

seq = 1×32

0 0 0 0 0 0 1 3 5 2 4 6 7 8 3 0 0 0 0 4 1 10 22 11 22 44 44 12 0 0

d = diff(seq ~= 0);
union(find(d==1), find(d==-1)+1)

ans = 1×4

6 16 19 29