Available with Spatial Analyst license.

Available with Image Analyst license.

Summary

Adds (sums) the values of two rasters on a cell-by-cell basis.

Discussion

When using an operator with a raster input, the result will be a raster. However, if all inputs are numbers, the result is a number.

When multiple operators are used in an expression, they are not necessarily executed in left-to-right order. The operator with the highest precedence value will be executed first. For more information, see the operator precedence table in Work with operators in Map Algebra. You can use parentheses to control the execution order.

The order of the input is irrelevant for this operator.

If both input values are integers, the output values will be integers; otherwise, the output will be floating-point values.

Another way to perform the addition operation is a += b, which is an alternative way to write a = a + b.

If both inputs are single-band rasters, or one of the inputs is a constant, the output will be a single-band raster.

If both inputs are multiband rasters, the operator will perform the operation on each band from one input, and the output will be a multiband raster. The number of bands in each multiband input must be the same.

If one of the inputs is a multiband raster and the other input is a constant, the operator will perform the operation against the constant value for each band in the multiband input, and the output will be a multiband raster.

If both inputs are multidimensional rasters with same number of variables, the operator will perform the operation for all slices with same dimension value, and the output will be a multidimensional raster. The variables in the inputs must have same dimensions or common dimension but no uncommon dimensions.

If both inputs have one variable but different names, set the matchMultidimensionalVariable geoprocessing environment to False to perform the operation.

If one of the inputs is a multidimensional raster and the other input is a constant, the operator will perform the operation for all slices for all variables against the constant value, and the output will be a multidimensional raster.

Parameters

 Operand Explanation Data Type in_raster_or_constant1 The input to which values will be added. If one of the input is a raster and the other is a scalar, an output raster is created with the scalar value being added to each cell in the input raster. Raster Layer | Constant in_raster_or_constant2 The input whose values will be added to the first input. If one of the inputs is a raster and the other is a scalar, an output raster is created with the scalar value being added to each cell in the input raster. Raster Layer | Constant

Code sample

+ (Addition) example 1 (Python window)

This sample adds two input rasters.

``````import arcpy
from arcpy import env
from arcpy.ia import *
env.workspace = "C:/iapyexamples/data"
outPlus = Raster("degs") + Raster("negs")
outPlus.save("C:/iapyexamples/output/outplus.img")``````
+ (Addition) example 2 (stand-alone script)

This sample adds two input rasters.

``````# Name: Op_Plus_Ex_02.py
# Description: Adds the values of two rasters on a cell-by-cell basis.
# Requirements: Image Analyst Extension

# Import system modules
import arcpy
from arcpy import env
from arcpy.ia import *

# Set environment settings
env.workspace = "C:/iapyexamples/data"

# Set local variables
inRaster1 = Raster("cost")
inRaster2 = Raster("degs")

# Execute Plus
outPlus = inRaster1 + inRaster2

# Save the output
outPlus.save("C:/iapyexamples/output/outplus")``````