Create signal block based on a threshold

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Angus Joyce
Angus Joyce 2019-9-10
回答： Sammit Jain 2020-1-27
Hi there,
I have a signal which is saved as a csv file. I'm trying to break up the signal into individual blocks of a fixed length (say 100 samples) for analysis (fft, wavelet, amplitude etc) when a threshold is crossed. If, the threshold was to be placed at 5, I still need the a bit before the threshold included in the block (say 30 of the 100 samples before the major peak, 70 after). How would i go about this, only getting 1 block output per signal pulse.
Many thanks in advance!
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回答（1 个）

Sammit Jain
Sammit Jain 2020-1-27
Hi Angus,
I'm assuming that the csv file has been imported into the MATLAB workspace. If you encountered issues while importing the csv, you may look at: https://www.mathworks.com/matlabcentral/answers/72545-how-to-import-csv-file-in-matlab
Let us say it had 600 samples, and it was broken down into 6 blocks of 100 samples each.
For the sake of this example, let us consider each block to be of length 10 samples.
Consider one such block B = [4 3 2 2 10 1 5 20 9 1].
B = [4 3 2 2 10 1 5 20 9 1];
idx = find(B > 5);
peak_idx = idx(1);
thresholded_sample = B(1:peak_idx-1);
In this case thresholded_sample will have [4 3 2 2]

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