Change color of overlapping waves with "fill-to-zero" mode

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Is there a straightforward way to reproduce the style of the attached plot in Igor Pro? In particular, where the red wave overlaps with the green wave, the color is white. I suspect there is an easy way to do this by arranging waves and choosing the correct mode/fill, but I haven't been able to figure it out. Any help is appreciated. I have Igor 7, so I can make one of the waves translucent; this approximates the effect I'm after, but I would prefer the look of the attached plot. 

 Example plot where overlapping waves are different color

With just two waves you could simply use fill-to-next with different colors for positive and negative values.

December 15, 2018 at 12:20 pm - Permalink

To do what you want without transparency, you need to splt the front (red) wave into two waves which add up to the value in the red wave. Here's a function that does that:

Function MakeOverlapWaves(frontWave, backWave)
    Wave frontWave // broken into two additional waves: one to be displayed on top of the other using add-to-next
    Wave backWave // the wave that "slices" the front wave into an aboveWave and a belowWave
    
    if( numpnts(frontWave) != numpnts(backWave) )
        DoAlert 0, "expects waves of the same length"
        return 0
    endif
    
    Duplicate/O frontWave, aboveWave, belowWave // should use variable names, but this is a demo
    belowWave = frontWave[p] > backWave[p] ? backwave[p] : frontWave[p]
    aboveWave = frontWave[p] - belowWave[p] 
    return 1
End

I've attached an image of the results compared to using transparency, as well as my demo experiment.

 
OverlappingDemo.png (97.77 KB) overlapIsWhite.pxp (39.24 KB)

December 16, 2018 at 02:34 pm - Permalink

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