topic Re: Return pixel position of minimum value for each zone? in ArcGIS Spatial Analyst Questions

Return pixel position of minimum value for each zone?

ChrisSnyder — Wed, 31 Jul 2013 16:45:55 GMT

I have a streamlink raster and a "value" raster that has floating point values. I want to return the pixel position of the minimum value for each zone.... Sort of like a zonal minimum, but instead of applying the minimum value to the entire zone, I just want to return the pixel(s) that have the minimum value of each zone (and tag the rest as NoData or some other value). I don't even need to return the minimum value - just return the pixel that has the minimum value and assign it a value of 1. I have a working method for doing this, but it requires converting my raster to points and then a bunch of extra steps along the way - pretty sloppy and slow.

I am looking for an elgant raster-based solution that is fast, since I have to do this process many times over via a Python script.

A graphical representation of a hypothetical zone (x = nodata)

input:  3 5 6 2 3 4 6 7 9 output: x x x 1 x x x x x

Any ideas?

Re: Return pixel position of minimum value for each zone?

ChrisSnyder — Wed, 31 Jul 2013 20:39:00 GMT

I got it:

Con(valueGrd == ZonalStatistics(strmLinkGrd, "VALUE", valueGrd, "MINIMUM", "DATA"), 1)

Re: Return pixel position of minimum value for each zone?

SteveLynch — Mon, 05 Aug 2013 13:57:07 GMT

Chris

Have a look at

http://arcpy.wordpress.com/tag/zonal-statistics/

Re: Return pixel position of minimum value for each zone?

ChrisSnyder — Mon, 05 Aug 2013 14:57:19 GMT

Thanks Steve - that's the same method I came up with too.