Expanding array from seconds to samples

Question

Anna Kasdan 2018-4-3

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/392432-expanding-array-from-seconds-to-samples

评论： Anna Kasdan 2018-4-4

I have an array (these are seconds of EEG data) that I want to expand to samples, where Fs=128.

bad_seconds = [1 2 11 13 14 15 17 18 22 24 26 27 37 47 48 50 57 58 70 75 90 118 120 144 145 147]

So for example, I would want the first two elements of the array to expand by 128 and look like this

bad_samples = [1:256 1208:1408.....]

I tried something like the following, but it doesn't get me the range that I want, just the start and end values and I would ideally just insert a colon between every other value for the range of samples!

   Fs = 128; 
   bad_samples_start = (bad_seconds * Fs)-128;
    bad_samples_end = bad_samples_start + 128;
    temp = [bad_samples_start; bad_samples_end];
    combined = temp(:)';

Any help would be appreciated, thanks! Still learning my way around Matlab things.

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Answer 1

David Fletcher 2018-4-3

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https://ww2.mathworks.cn/matlabcentral/answers/392432-expanding-array-from-seconds-to-samples#answer_313378

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Something like this?

bad_seconds = [1 2 11 13 14 15 17 18 22 24 26 27 37 47 48 50 57 58 70 75 90 118 120 144 145 147]
t1=bad_seconds*128-128;
t2=t1+127;
ranges=[t1;t2]
combined=[]
for iter=1:size(ranges,2)
    combined=[combined ranges(1,iter):ranges(2,iter)];
end

A few things to note: The combined array is grown dynamically. This is generally frowned upon, but unless this section of code becomes noticeably slow, I wouldn't worry about it.

I've slightly amended the formula for the range end point as there was an overlap between consecutive ranges. I was also slightly unsure whether you wanted the start of the range to be one more than defined by your formula (bad_seconds*128-127 rather than bad_seconds*128-128), but I've left that as per your formula