ArcMap

Round Down

Available with Spatial Analyst license.

Summary

Returns the next lower integer value, just represented as a floating point, for each cell in a raster.

Illustration

Round Down illustration
OutRas = RoundDown(InRas1)

Usage

  • Input values can be positive or negative.

  • The output raster from this tool is always floating-point type, regardless of the input value type.

  • If the input number has any values to the right of the decimal point, the output will be assigned the next lower integer value, but will be represented as a floating point number with no decimal portion. For example:

        Input   Output
     5.3     5.0
     4.9     4.0
     3.0     3.0
     6.5     6.0
    -0.2    -1.0
    -2.8    -3.0

  • There is a difference between the Int tool and the Round Down tool. For example, given the following two values, Int always truncates the number:

    • 1.5 becomes 1
    • -1.5 becomes -1

    while for the same two values, Round Down returns:

    • 1.5 becomes 1.0
    • -1.5 becomes -2.0

    Another difference is that Round Down outputs floating-point values, while Int only outputs integer values.

  • See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool.

Syntax

RoundDown (in_raster_or_constant)
ParameterExplanationData Type
in_raster_or_constant

The input values to be rounded down.

In order to use a number as an input for this parameter, the cell size and extent must first be set in the environment.

Raster Layer; Constant

Return Value

NameExplanationData Type
out_raster

The output raster.

The cell values are the result of rounding down the input values.

Raster

Code sample

RoundDown example 1 (Python window)

This example rounds the values in the input raster to the next lower integer value and outputs a floating-point raster.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outRoundDown = RoundDown("gwhead")
outRoundDown.save("C:/sapyexamples/output/outrd")
RoundDown example 2 (stand-alone script)

This example rounds the values in the input raster to the next lower integer value and outputs a floating-point raster.

# Name: RoundDown_Ex_02.py
# Description: Returns the next lower whole number for each cell in a raster
# Requirements: Spatial Analyst Extension

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

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

# Set local variables
inRaster = "gwhead"

# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")

# Execute RoundDown
outRoundDRaster = RoundDown(inRaster)

# Save the output 
outRoundDRaster.save("C:/sapyexamples/output/outrounddown")

Environments

Licensing information

  • ArcGIS Desktop Basic: Requires Spatial Analyst
  • ArcGIS Desktop Standard: Requires Spatial Analyst
  • ArcGIS Desktop Advanced: Requires Spatial Analyst

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