| Operand | Explanation | Data Type |
in_raster_or_constant1 | The input from which to subtract the values in the second input. If the first input is a raster and the second is a scalar, an output raster is created with each input raster value being subtracted by the scalar value. | Raster Layer | Constant |
in_raster_or_constant2 | The input values to subtract from the values in the first input. If the first input is a scalar and the second is a raster, an output raster is created with each input raster value being subtracted from the scalar value. | Raster Layer | Constant |
Available with Spatial Analyst license.
Available with Image Analyst license.
Summary
Subtracts the value of the second input raster from the value of the first input raster on a cell-by-cell basis.
Illustration
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 Working with operators in Map Algebra. You can use parentheses to control the execution order.
The order of the input is relevant 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 subtraction operator 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
Code sample
This sample subtracts the values of the second input raster from the first.
import arcpy
from arcpy import env
from arcpy.ia import *
env.workspace = "C:/iapyexamples/data"
outMinus = Raster("degs") - Raster("negs")
outMinus.save("C:/iapyexamples/output/outminus")This sample subtracts the values of the second input raster from the first.
# Name: Op_Minus_Ex_02.py
# Description: Subtracts the value of the second input raster from the
# value of the first input raster 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("degs")
inRaster2 = Raster("negs")
# Execute Minus
outMinus = inRaster1 - inRaster2
# Save the output
outMinus.save("C:/iapyexamples/output/outminus.tif")