topic Re: Raster function equivalent of Build Raster Attribute Table in ArcGIS Image Analyst Questions

Raster function equivalent of Build Raster Attribute Table

MervynLotter — Fri, 10 Dec 2021 13:55:04 GMT

Hi there

I would like to include the output of a raster function into the Tabulate Area GP tool, but my raster function output does not have an attribute table. If it were a traditional raster, then I would have run the Build Raster Attribute Table gp tool to create one. Is there a raster function equivalent or is there a different approach to follow? I need to work with categorical data.

Thanks.

Re: Raster function equivalent of Build Raster Attribute Table

DanPatterson — Fri, 10 Dec 2021 15:01:20 GMT

what kind of raster is it? normally a float raster has to be converted to an int raster in order to build a raster attribute table. The only thing that I can find to do zonal crosstab (aka counts) is xarray's zonal.crosstab, it is shipped with Pro 2.9

xrspatial.zonal.crosstab — xarray_spatial 0.3.0+g9a8909e-dirty documentation (xarray-spatial.org)

it produces a pandas df (pandas is also installed)

Re: Raster function equivalent of Build Raster Attribute Table

DanPatterson — Fri, 10 Dec 2021 15:16:21 GMT

Of course you can do it in numpy using RasterToNumPyArray to get a raster out to an array

import numpy as np a = np.random.randint(0, 4, size=100).reshape(10, 10) b = np.random.randint(4, 8, size=100).reshape(10, 10) ab = np.vstack((a.ravel(), b.ravel())).T u, cnts = np.unique(ab, return_counts=True, axis=0) a # -- zone raster array([[0, 1, 0, 2, 2, 1, 2, 0, 1, 0], [0, 3, 0, 2, 1, 3, 0, 0, 2, 0], [0, 1, 2, 1, 2, 3, 1, 0, 0, 3], [2, 1, 1, 2, 0, 0, 1, 3, 3, 2], [0, 0, 2, 2, 0, 0, 0, 0, 1, 1], [3, 1, 2, 0, 0, 1, 2, 1, 1, 0], [0, 0, 3, 0, 3, 1, 2, 3, 0, 0], [0, 3, 3, 1, 3, 1, 3, 1, 2, 3], [3, 0, 0, 1, 3, 2, 2, 1, 0, 0], [1, 1, 0, 2, 3, 3, 1, 1, 1, 1]]) b # -- values raster array([[5, 6, 4, 6, 4, 7, 7, 6, 6, 4], [6, 4, 6, 4, 7, 6, 4, 7, 4, 6], [4, 4, 7, 5, 4, 7, 6, 7, 5, 4], [7, 6, 5, 6, 7, 4, 7, 4, 5, 5], [4, 7, 4, 6, 7, 5, 5, 4, 4, 7], [4, 6, 7, 4, 7, 6, 6, 6, 6, 4], [4, 6, 7, 6, 4, 7, 4, 5, 6, 4], [4, 6, 6, 6, 4, 4, 4, 4, 6, 5], [4, 7, 7, 7, 6, 5, 5, 6, 7, 5], [4, 4, 5, 5, 4, 6, 5, 5, 6, 6]]) u # -- unique combinations array([[0, 4], [0, 5], [0, 6], [0, 7], [1, 4], [1, 5], [1, 6], [1, 7], [2, 4], [2, 5], [2, 6], [2, 7], [3, 4], [3, 5], [3, 6], [3, 7]]) cnts # -- counts per combination array([12, 6, 7, 9, 6, 4, 12, 6, 6, 4, 5, 4, 9, 3, 5, 2], dtype=int64)

Re: Raster function equivalent of Build Raster Attribute Table

curtvprice — Fri, 10 Dec 2021 16:22:03 GMT

My understanding is that raster functions are on the fly animals that process at a dynamic resolution and window, so seems to me the idea of a raster table wouldn't really apply, as you need a complete dataset to calculate cell counts and a list of unique values.