Chaining successive Time-based epoching

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heuheujai
Posts: 3
Joined: Fri Jun 10, 2016 9:57 am

Chaining successive Time-based epoching

Post by heuheujai »

Hi,

I was trying to create a scenario involving multiple uses of "Time Based Epoching" in a raw.
More precisely, I understood that the output of "Time Based Epoching" is slices of signal with possible overlap: this is not exactly a new continuous signal then.
However, if I use then a Box like Signal Average, I understood that the output was a regular signal again.
For instance, let's say I do "Time Based Epoching" with length 2s every 1s, followed by Signal Average, I should have a regular signal with sample value every second, on which I should be able to apply Time Based Epoching again.
But when I try "Mediane" on the new output signal, and I try to display it, I get nothing, with an error involving 0 sampling rate.
Note that if I used "Epoch Average", it works but there's apparently no Epoch Median, and in any case I would like to be able to do multiple successive epoching.

My question is: is it possible to convert the output of the "Time Based Epoching" + some processing that turns slices of signal into a unique scalar value (like signal average) back to a regular signal, on which it is possible to apply any Box that accepts regular signal as Input, like "Time Base Epoching" again for instance. Or is there a work around ?

Thanks in advance!

Heuheujai

heuheujai
Posts: 3
Joined: Fri Jun 10, 2016 9:57 am

Re: Chaining successive Time-based epoching

Post by heuheujai »

Any thoughts by any chance ?

jtlindgren
Posts: 775
Joined: Tue Dec 04, 2012 3:53 pm
Location: INRIA Rennes, FRANCE

Re: Chaining successive Time-based epoching

Post by jtlindgren »

Hi, I can't think of a way to do what you want with the current boxes. It might be possible to develop a generic box in C++ to merge overlapping epochs back to a continuous signal, but what would its operating principle be? Lets say it gets time-overlapping chunks as input. Whats supposed to be in the output?

Example: we have overlapping block stream with time range stamps [0,1]; [0.5,1.5]; [1,2]; [1.5,2.5]; [2.0,3.0], etc... what does the box output? what content per chunk, what time range for chunk, what sampling rate?


Cheers,
Jussi

heuheujai
Posts: 3
Joined: Fri Jun 10, 2016 9:57 am

Re: Chaining successive Time-based epoching

Post by heuheujai »

Hi Jussi,

thanks for your answer.
You're right: in the general case, it does not really make sense, there's no obvious way to turn overlapping chunks into a continuous signal.

However, as I specified, if you add another processing on the overlapping chunks like "epoch average" that turns each chunk into one single value, it becomes a signal again, in that case it would be simple to cast it from epoch to signal.
For instance, in your example, if I do epoch average, the output is the average value of each block, the sample rate 2Hz, and the time index would be the middle point of each block.

It would also be possible if the epochs are just a division of the initial signal (no overlapping, no gap).

Anyway, I understand it's not possible with the existing boxes. Thanks again.

Best,

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