newtfish

Im trying to detect when a number changes, but only when it has changed 10 times within a period of time.

I'm thinking change object, thresh and/or zl queue could be used to do this, but im struggling to make it work.

For instance, I would like to ignore when there are multiple occurrences of the same number

But if there are 10 different numbers within a given period, I would like to recognise this - e.g.

Would be grateful if anyone has any interesting ways of getting around this problem.

But if there are 10 different numbers within a given period, I would like to recognise this - e.g. 

change-object-detect-multiple-changes

From the other thread I know that you are looking for data reduction (in both amount and speed). So you could think about it as smoothing as well. In your case a simple average of a block of numbers could be sufficient:

If you are more interested in avoiding big jumps between output values you could refer to a moving average approach. Advantage is smaller jumps, disadvantage your actual output value might be further away from your current data set (as it can take a longer "history" of data into account)

Building on what Jan said: you might also try a median filter. It is unaffected by extreme outliers and, if using an odd length, always produces a value which is on the stream. (e.g. Zl.stream 9 -> zl.median)

Posting from my phone, so can't check out other poster's solution, but you can find out whether a list has any doubled values by sorting it and then comparing it to a rotated by 1 version, then looking for ones. Something like zl.stream 12 into zl.sort into zl.rot 1 with sorted version into vexpr $i1==$i2 into zl.sum into == 0. That should be true IFF there are no repeated values.

Building on what Jan said: you might also try a median filter.  It is unaffected by extreme outliers and, if using an odd length, always produces a value which is on the stream.  (e.g. Zl.stream 9 -> zl.median)

Posting from my phone, so can't check out other poster's solution, but you can find out whether a list has any doubled values by sorting it and then comparing it to a rotated by 1 version, then looking for ones.  Something like zl.stream 12 into zl.sort into zl.rot 1 with sorted version into vexpr $i1==$i2 into zl.sum into == 0.  That should be true IFF there are no repeated values.


I've tried each one of these examples and they all work really well and I've learnt quite a few new things along the way as well. Many thanks.

change object - detect multiple changes