topic Standardising rasters in arcpy in Python Questions

Standardising rasters in arcpy

DanielFuller — Fri, 14 May 2021 13:15:28 GMT

Hello

I have to to standardise some rasters using a loop and following equation

X1= (X - X.min())/(X.max()-X.min())

where X is the original dataset, and X1 the new standardized dataset, which has a minimum value of 0 and a maximum value of 1.

I was wondering how I would go about doing this? the current code I have is

for calc in projected_rast: print calc minLSTresult = arcpy.GetRasterProperties_management(calc, "MINIMUM") maxLSTresult = arcpy.GetRasterProperties_management(calc, "MAXIMUM") standardised = ((calc - minLSTresult)/(maxLSTresult-minLSTresult)) standardised.save()

were projected_rast is a list of strings to my rasters

Re: Standardising rasters in arcpy

DanPatterson — Fri, 14 May 2021 22:58:16 GMT

What does it yield?

Are you using ArcMap? (your print statement suggests python 2.7)

Do you have any null areas/values?

Of course you could use RasterToNumPyArray and use numpy to do the work quickly.

import numpy as np a = np.arange(0, 12.).reshape(4, 3) a array([[ 0., 1., 2.], [ 3., 4., 5.], [ 6., 7., 8.], [ 9., 10., 11.]]) a_min = np.nanmin(a) a_max = np.nanmax(a) a_stand = (a - a_min) / (a_max - a_min) a_stand array([[0. , 0.09090909, 0.18181818], [0.27272727, 0.36363636, 0.45454545], [0.54545455, 0.63636364, 0.72727273], [0.81818182, 0.90909091, 1. ]])

Re: Standardising rasters in arcpy

Luke_Pinner — Sat, 15 May 2021 00:54:03 GMT

a Raster object has maximum and minimum properties (if statistics have been calculated).

for calc in projected_rast: print(calc) raster = arcpy.Raster(calc) minLSTresult = raster.minimum maxLSTresult = raster.maximum standardised = ((raster - minLSTresult)/(maxLSTresult-minLSTresult)) standardised.save()

Re: Standardising rasters in arcpy

DanielFuller — Sat, 15 May 2021 21:43:10 GMT

Worked perfectly 🙂