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# Normal distribution raster creation

Release 9.3

Print all topics in : "Raster Creation"

Note: This topic was updated for 9.3.1.

The Create Normal Raster (or Normal in Map Algebra) tool creates an output raster in which the count of the resulting values produces a normal distribution around a mean of zero and a standard deviation of one. The mean and standard deviation can easily be changed. To create a raster of values with a normal distribution characterized by a mean of 39 and a standard deviation of 2.5, you would need to multiply the resulting raster by 2.5, then add 39. Using Map Algebra, you can enter the following expression:

`    OutRas = normal() * 2.5 + 39`

In the output raster in the above expression, 95 percent of the output values will be within 36.5 and 41.5.

Before running the Map Algebra Normal function, you must set the extent of the Analysis window and you should set the desired cell size.

Example
Following is an output raster with a normal distribution of values created with the Map Algebra Normal function.

Expression: OutRas = NORMAL()

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