# Raster Calculator syntax

I have two rasters depicting climate in two periods and I want to compare their values.

I want to create a third raster returning:

Values of raster 1 are within the minimum and maximum values of raster 2.

and fourth raster:

Values of raster 1 are within the 2.5 % and 97.5 % percentile of raster 2.

I have never worked with raster calculator and I do not know the syntax.

• I don't know the exact syntax for raster calculator either, but I suggest you'd start with making 4 'compare' rasters from raster 2, one with the maximum value in every cell, one with the minimum, one with the 2.5% value, and one with the 97.5% value, and then compare raster 1's values with these. Nov 13, 2014 at 10:25

The raster calculator syntax for you third raster is the following

``````Con( ("raster1" < "raster2".maximum) &  ("raster1" > "raster2".minimum) , 1, 0)
``````

there is no built in method to get the percentiles, so you should compute them based on the histogram of you image and manually enter the values in the raster calculator. But you can approximate (if your distribution is close to a Gaussian) using mean + 1.96 * standard deviation

``````Con( ("raster1" < ( "raster2".mean + 1.96 * "raster2".standardDeviation ) ) &  ("raster1" > ( "raster2".mean - 1.96 * "raster2".standardDeviation ) ) , 1, 0)
``````
• Are you sure you can utilize the `.maximum` or `.minimum` methods in the raster calculator? I thought you had to generate separate raster objects outside the RC in order for these methods to be utilized.
– Aaron
Nov 13, 2014 at 12:28
• tested with ArcGIS 10.1 and 10.2, for 10.0 I don't know, and for 9.x it doesn't work. Nov 13, 2014 at 12:37
• +1 This is great. My only sticking point is that it assumes a Gaussian distribution and so few of the phenomena that we deal with actually are normal. Does ArcGIS not have a tool to convert a raster to a cumulative distribution function ala uoguelph.ca/~hydrogeo/Whitebox/Help/… ? If so, that could be used to get the 2.5 and 97.5 percentiles. Nov 13, 2014 at 14:50
• Thank you, radouxju, you saved my bachelor thesis, I used only the first syntax as all distributions were far from Gaussian. Thanks
– Jane
Nov 13, 2014 at 15:01
• If this answers your question, you should click the checkmark under the rating in the upper left of the answer to indicate that. Nov 13, 2014 at 16:38