Effacer les filtres
Effacer les filtres

Find duration of signal

2 vues (au cours des 30 derniers jours)
Marc Elmeua
Marc Elmeua le 9 Sep 2020
Commenté : Xavier le 10 Sep 2020
I have a set of signals that due to some unknown error have been acquired with millions of empty datapoints. Is there a way I can automatically detect the moment the signal ends so I can delete everything from that point onwards?
Thanks everyone.
  4 commentaires
Star Strider
Star Strider le 9 Sep 2020
There are no actual ‘missing’ values, just a very low amplitude signal after about element 40:
T1 = readtable('sampledata.csv');
figure
semilogy(abs(T1{:,1}))
grid
producing:
That would appear to be legitimate data.
.
Xavier
Xavier le 10 Sep 2020
This depends on how you define legitimate data, if you unplug a probe/sensor from an oscilloscope it will continue to display numbers and a waveform. If you're trying to measure a signal then it is fair to call recorded noise invalid data

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Réponse acceptée

Xavier
Xavier le 10 Sep 2020
Something like this may work for you
Raw data:
data = readmatrix('sampledata.csv');
avgdat = movmean(abs(data), 5);
threshold = 0.01;
data(avgdat < threshold) = [];
plot(data)
  2 commentaires
Marc Elmeua
Marc Elmeua le 10 Sep 2020
This worked perfectly!! thanks a lot.
Xavier
Xavier le 10 Sep 2020
No problem!

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Plus de réponses (1)

Steven Lord
Steven Lord le 9 Sep 2020
If the empty data points are represented by NaN then find the 'last' 1 element of the vector that isfinite.
x = [1:10 NaN(1, 5)]
find(isfinite(x), 1, 'last')
If the vector has no missing data inside it, you could instead just rmmissing.
rmmissing(x)
  1 commentaire
Marc Elmeua
Marc Elmeua le 9 Sep 2020
Thanks for the reply! The missing values aren't really missing in the matlab file. They are missing in the original data collection software but as soon as you retrieve them, they turn into zeros so this code will not work :(
I'm in touch with the developers of the software but they still haven't been able to solve this.

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