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Finding Indices of Zeroes Following Non-Zero Elements in MATLAB

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Sabella Huang
Sabella Huang 2023 年 6 月 30 日
コメント済み: Bruno Luong 2023 年 7 月 7 日
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

回答 (4 件)

Chunru
Chunru 2023 年 6 月 30 日
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

Harshavardhan Putta
Harshavardhan Putta 2023 年 6 月 30 日
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!

Anamika
Anamika 2023 年 7 月 7 日
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

Bruno Luong
Bruno Luong 2023 年 7 月 7 日
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
  1 件のコメント
Bruno Luong
Bruno Luong 2023 年 7 月 7 日
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

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