Round Down (Spatial Analyst)

Summary

Returns the next lower whole number for each cell in a raster.

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 a number has any values to the right of the decimal point, the output will be assigned the next lowest whole value. 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.

Syntax

RoundDown (in_raster_or_constant)

Parameter	Explanation	Data 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

Name	Explanation	Data Type
out_raster	The output raster. The cell values are the input values converted to integers by rounding down to the next lower whole number.	Raster

Code Sample

RoundDown example 1 (Python window)

This example rounds the values in the input raster to the next lower whole number.

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 whole number.

# 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

Cell Size, Current Workspace, Mask, Output Coordinate System, Extent, Scratch Workspace, Snap Raster

Licensing Information

ArcGIS for Desktop Basic: Requires Spatial Analyst

ArcGIS for Desktop Standard: Requires Spatial Analyst

ArcGIS for Desktop Advanced: Requires Spatial Analyst