Excluding "NoData" from raster percentile calculation.

anTonialcaraz — Sun, 12 Dec 2021 07:49:28 GMT

Hi,

I'm trying to calculate percentiles out of a floating point raster. It works but it includes NoData in the calculation so I'm not getting what I need.

I wonder if someone knows how to exclude the "NoData" from the calculation.

Many thanks

env.workspace = r"D:\PROGRAMMES\LFP_Source_Rocks\ArcGIS\00_LFP_GLOBAL\00_UPWELLING\OUTPUT_Test.gdb"
raster = env.workspace + "\\" + "percentile"
array = arcpy.RasterToNumPyArray(raster)
array = scipy.sort(array)
per = 10
a = scipy.percentile(array,per)
print a

Re: Excluding "NoData" from raster percentile calculation.

DanPatterson_Retired — Thu, 16 Jul 2015 15:01:20 GMT

You have many options, depending on what your nodata values were converted to,

There is Release Notes — NumPy v1.9 Manual if you are using Numpy 1.9 or your version supports it

EDIT

these comments were for means...but whatever, there is a nan_stat for every equivalent o any stat but you can create masked arrays or use where functions to mask nodata values in a raster.

np.nanmean numpy.nanmean — NumPy v1.10.dev-19c3cf1 Manual
create a masked array and use numpy.ma.mean — NumPy v1.9 Manual
plus oodles of other where you can use np.where( myarray > whatever is 'null') then take the mean

so check the details of how you created RasterToNumPyArray—Help | ArcGIS for Desktop and the option you used regarding nulls

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Excluding "NoData" from raster percentile calculation.

Re: Excluding "NoData" from raster percentile calculation.