Feature aggrator

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Anne
Posts: 13
Joined: Thu Dec 09, 2010 3:34 pm

Feature aggrator

Post by Anne »

Hi!
I have to use the "Feature Aggregator" box, but it isn't for me clear what types of features are extracted.
I have seen some examples and usually the "Feature Aggregator" box is preceded from "Signal DSP" box (doing the x*x), the "Signal Average" box and another "Signal DSP" box (doing log(1+x) ), but i don't get the meaning.

Thank you in advance!!

Anne

lbonnet
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Posts: 417
Joined: Wed Oct 07, 2009 12:11 pm

Re: Feature aggrator

Post by lbonnet »

Hi Anne,

In fact the Feature Aggregator, as its name suggests, doesn't extract anything.
It reads incoming features (you can add as many feature inputs as you want), and when one feature has been received on every input, the box aggregates them in one vector.
Basically, it's just a conversion in another stream format : the feature vector.

This box is always used pior to classification boxes :
- Before the Classifier trainer to produce the feature vectors that "feed" the trainer on each class.
- before the Classifier processor to produce the feature vector processed by the classifier to predict the corresponding class.
have seen some examples and usually the "Feature Aggregator" box is preceded from "Signal DSP" box (doing the x*x), the "Signal Average" box and another "Signal DSP" box (doing log(1+x) ), but i don't get the meaning.
Here you extract one feature : log(1+x²) where x is the incoming (filtered) signal. This is called logarithmic band power.
Thus the feature aggregator aggregates only... one feature for the classification.

I hope this is clear enough :)

Laurent-
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Checkout my (old) blog for some OpenViBE tips & tricks : here !

Anne
Posts: 13
Joined: Thu Dec 09, 2010 3:34 pm

Re: Feature aggrator

Post by Anne »

Ok,
i begin to understand....
But if I utilize more than 1 channels, how is this managed? They are put in a vector? so if I use more than a feature and more than a channel, it comes out a matrix of features?

Thank you :)

Anne

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