Normalizing raster using raster calculator raises TypeError

Question

In ArcGIS 10.1 I'm trying to normalize a section of a DEM (digital elevation model) from original values to values ranging from 0 to 100. First I clipped the raster DEM with an irregulary shaped polygon. Now I'm tying to change all the values to a range of 0 to 100 for further analysis.

I'm using the Raster calculator tool with this equation:

("DEM" - min("DEM")) * 100 / (max("DEM") - min("DEM")) + 0 

I keep getting TypeError: 'Raster' object not iterable. This is the log I get:

   ERROR 000539: Error running expression: rcexec() 
    Traceback (most recent call last):
      File "<expression>", line 1, in <module>
      File "<string>", line 5, in rcexec
    TypeError: 'Raster' object is not iterable

I also tried running the command on the unclipped raster, unsuccessfully.

Answer 1

The builtin python min() and max() functions operate only on python iterables (i.e lists, tuples, etc.) and return the smallest/largest item in the iterable. They do not return the minimum/maximum value of a Raster object which is why a TypeError was raised.

You need to use the Raster.minimum and Raster.maximum properties.

For example:

("dem" -"dem".minimum) * 100 / ("dem".maximum - "dem".minimum) + 0 

Note: This will work as long as you have already calculated statistics for the raster, otherwise it will fail as "raster".minimum will return None.