Script Zonal statistics percentiles, using Float rasters

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03-03-2016 09:43 AM
BrianPowell
New Contributor II

Branched from: Re: Script Zonal statistics percentiles, using Float rasters

Hello,

I'm trying to do the exact same thing for 25, 50, and 75 percentiles.  I have an integer DEM and a set of continuous polygons.  Here is the error I'm getting:

Traceback (most recent call last):

  File "C:\Python27\ArcGIS10.3\Lib\percentiles.py", line 100, in <module>

    pixval =  GetPixelValueForPercentile(dct_per, perc_dec)

  File "C:\Python27\ArcGIS10.3\Lib\percentiles.py", line 10, in GetPixelValueForPercentile

    return pix_val

UnboundLocalError: local variable 'pix_val' referenced before assignment

I am not a python programmer, any insight is most appreciated.  I've attached the script with the changes I made, which were only the list of percentiles (line 25) and the paths to my datasets.  Ideally, if it's possible, I would like to run this on a float raster instead of an integer raster.

Much thanks,

Brian

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Accepted Solutions
XanderBakker
Esri Esteemed Contributor

As Dan Patterson​ states, most likely you have a polygon with a hole in it. The Nonetype point indicates the start of an inner ring. To avoid this you could use the code posted here:

https://community.esri.com/thread/95403#555075

Instead of using ExtractByPolygon it uses ExtractByMask.

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12 Replies
XanderBakker
Esri Esteemed Contributor

You're not using the latest script posted in this thread. Line 4 should read.

pix_val = sorted(dctper.keys())[0]

... but is missing in your script.

To run this on float raster data, would require a different approach. Only integer rasters have an attribute table and this is used in the script to determine the percentiles. However, one could implement a procedure that takes an float raster as input, converts it to integer (applying a multiplication factor to reduce the loss of precision) and apply the factor in the results too.

What is the data range of the float raster you have?

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BrianPowell
New Contributor II

The data range of the float raster is -26.9159 to 334.042.

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XanderBakker
Esri Esteemed Contributor

What precision are you trying to obtain. Would in this case a multiplier by 10 be sufficient, the range would be changed at the end of the run to -26.9 to 334.0. You could test this manually by using the Raster Calculator (in Spatial Analyst Tools\Map Algebra) and use a formula like:

BrianPowell
New Contributor II

The script ran a lot longer now that I incorporated your prior suggestions.  Now I am getting this at line 60.

Traceback (most recent call last):

  File "C:\Python27\ArcGIS10.3\Scripts\percentiles_edit.py", line 60, in <module>

    x, y = pnt.X, pnt.Y

AttributeError: 'NoneType' object has no attribute 'X'


Failed to execute (Percentiles).

Failed at Thu Mar 03 13:35:22 2016 (Elapsed Time: 7 minutes 36 seconds)

Any thoughts?

Much thanks,

Brian

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BrianPowell
New Contributor II

Hello Xander,

I like the idea of using a multiplier and converting to an integer raster as a work around, that will work fine for the float issue.  I am still getting the error on line 60:

x, y = pnt.X, pnt.Y

AttributeError: 'NoneType' object has no attribute 'X'

This is happening after it has already processed a handful of polygons.  I ran the check geometry and repair geometry tools to check for null geometries and the feature class seems fine.  Any ideas of why it may be erring out?

Thanks,

Brian

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DanPatterson_Retired
MVP Esteemed Contributor

do you have polygons with holes? a polygon with a hole will have a null separater between the inner and outer parts.  This case will complicate the process... then try a multipart polygon with multiple holes and you are pushing towards a full implementation of geometry checks and processing. 

XanderBakker
Esri Esteemed Contributor

As Dan Patterson​ states, most likely you have a polygon with a hole in it. The Nonetype point indicates the start of an inner ring. To avoid this you could use the code posted here:

https://community.esri.com/thread/95403#555075

Instead of using ExtractByPolygon it uses ExtractByMask.

BrianPowell
New Contributor II

Thank you guys both for your help and suggestions.  I was able to get it to run overnight and used a 100x multiplier.  This is great.

Sincerely,

Brian

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XanderBakker
Esri Esteemed Contributor

Glad to hear that it worked. Did you use the code with ExtractByMask or ExtractByPolygon?

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