How to cut out specific segments from a signal?

Question

Rafael Cordero 2017-1-30

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https://ww2.mathworks.cn/matlabcentral/answers/322556-how-to-cut-out-specific-segments-from-a-signal

评论： Star Strider 2023-12-18

采纳的回答： Star Strider

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Hi all,

Im going nuts. This should be really easy but i've been stuck on it for days.

Let's say I have a signal (vector) x. There are certain parts of x I want removed/extracted so that I leave behind a shorter version of x, without these parts.

I have two vectors defining these unwanted parts. One that defines that start position (remove_start) and another the end position (remove_end).

So the vectors look like:

x = [x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x ...]

remove_start= [11 26 ...] remove_end= [15 31 ...]

I want to get rid of the bold segments in order to get x = [x x x x x x x x x x x x x x], so sticking the non bold bits together. 'x' can take any (real) number.

The problem arises from the fact that when I do something like x(remove_start(i):remove_end(i))=[]; I screw up the timings of remove_start and remove_end. I've tried so many different ways of doing this but none seem to work.

The current way im doing it is:

cut_lag=0;

for i=1:length(remove_start)

    x(remove_start(i)-cut_lag(i):remove_end(i)-cut_lag(i))=[];
    cut_lag(i+1)=cut_lag(i)+remove_end(i)-remove_start(i);

end

So the idea is to keep track of my cutting out the non-wanted bits has shifted the remaining remove times.

This seems to work for the start of x but it eventually degrades and it ends up cutting out the wrong parts...

Plsss helps, thanks so much!!

R

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Answer 1

Star Strider 2017-1-30

1
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https://ww2.mathworks.cn/matlabcentral/answers/322556-how-to-cut-out-specific-segments-from-a-signal#answer_252628

在 MATLAB Online 中打开

If I understand correctly what you want to do, I would begin your loop at the end of the vector and move toward the beginning. That way, you don’t disrupt the other indices.

Something like this:

for i = length(remove_start):-1:1

I didn’t actually run your code, but this is the usual method of removing array elements in a loop without compromising the existing array references.