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Easy way to mask waves?

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amellnik January 2, 2012 - 11:41
Posts: 5
 Joined: 2009-07-09
 Location: United States

It seems like there should be a really easy way to mask waves, but I haven't been able to figure one out so far. For example, I might have to waves of the same length and I would like to delete all the points from the first wave where the corresponding point on the second wave is zero. The way I've been doing this so far is embarrassingly hackey:

targetwave = targetwave/(maskwave==0)
WaveTransform zapINFs targetwave
WaveTransform zapNaNs targetwave // 0/0 = NaN

This has the obvious problem that it gets rid of any NaNs and INFs that should be in targetwave. What's the proper way to do this? Thanks

-Alex
jtigor January 2, 2012 - 15:19
Posts: 177
 Joined: 2007-09-04
 Location: United States

Alex,

How about something like this?

Function DeletePointsInWave(w, wMask)
	Wave w         //wave to have points deleted
	Wave wMask     //comparison wave; zeroes here will delete corresponding points in w
 //w and wMask are assumed to be same length
 
	Variable vNumPoints
	Variable index
 
	vNumPoints = DimSize(w,0)
 
//have to do this from last point to first otherwise deleting points will change index of all points forward	
	for(index =  vNumPoints - 1; index >= 0; index -= 1)
		if(wMask[index] == 0)
			DeletePoints  index, 1, w
		endif
	endfor
End

My quick test shows that any point in wmask with a value of zero will cause the corresponding point in w to be deleted. There is no error checking, so watch out if it behaves unexpectedly. Hope this is what you have in mind.
awirsing January 8, 2012 - 00:48
Posts: 134
 Joined: 2007-09-19
 Location: Germany

Extract/O targetwave, targetwave, maskwave!=0 should also work. Be careful, targetwave is being overwritten! To avoid this, use a new name for destwave.
A
skleijn January 9, 2012 - 02:27
Posts: 3
 Joined: 2011-08-16
 Location: Netherlands

I'm trying something similar: I would like to use a piece of code that extracts a portion of a particular wave and use that portion to fill a new wave, rather than 'edit'-ing that wave and selecting the portion by mouse and ctrl+C&V. I would like to do something like the following:

Make /N=(pcsr(B)-pcsr(A)) copyWave
copyWave=sourceWave[pcsr(A):pcsr(B)]

however that does not work. What would be the proper code to do this?
aclight
 January 9, 2012 - 07:11
Posts: 563
 Joined: 2007-03-01
 Location: United States

skleijn wrote:
I'm trying something similar: I would like to use a piece of code that extracts a portion of a particular wave and use that portion to fill a new wave, rather than 'edit'-ing that wave and selecting the portion by mouse and ctrl+C&V. I would like to do something like the following:
Make /N=(pcsr(B)-pcsr(A)) copyWave
copyWave=sourceWave[pcsr(A):pcsr(B)]

however that does not work. What would be the proper code to do this?

Duplicate/R=[pcsr(A), pcsr(B)] sourceWave, copyWave
skleijn January 16, 2012 - 05:16
Posts: 3
 Joined: 2011-08-16
 Location: Netherlands

Perfect, thank you!
amellnik May 17, 2012 - 10:37
Posts: 5
 Joined: 2009-07-09
 Location: United States

Sorry for the late reply -- thanks for all the suggestions!
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