NDVI: Normalized Difference Vegetation Index Function

In griffithdan/grassmap: Stable Terrestrial Carbon Isoscape Package

Description

This function calculates the NDVI for the given extent based on remotely sensed reflectance values for Red and Near Infared (NIR) bands. The function removes any NA and negative values, and multiplies NDVI values by 10000.

Usage

NDVI(NIRstack, REDstack, NAValue, scalefactor, filename = '', ...)

Arguments

NIRstack	RasterStack or RasterBrick with the remotely sensed Near Infared (NIR) band reflectance values. Must have corresponding layers with REDstack input.
REDstack	RasterStack or RasterBrick with the remotely sensed visible red band reflectance values. Must have corresponding layers with NIRstack input.
NAValue	value to be set as NA in input layers
scalefactor	factor to scale NDVI output by
filename	Character. Output filename (optional)
...	additional arguments for writing files as in writeRaster

Details

It is important to perform any spatial resizing of reflectance data prior to running this function.

Value

RasterBrick

Author(s)

Sydney M Firmin

Examples

##load in NIR Reflectance Stack
##data("MODIS_NIR")
##load in Red Reflectance Stack
##data("MODIS_Red")

##aggregate reflectance layers and resample to match final output prior to calculating NDVI
##MODIS_NIR_ag <- aggregate(MODIS_NIR, fact=9, fun=mean, expand=TRUE)
##MODIS_NIR_rs <- resample(MODIS_NIR_ag, CO_C3Crop, method="bilinear")
##MODIS_Red_ag <- aggregate(MODIS_Red, fact=9, fun=mean, expand=TRUE)
##MODIS_Red_rs <- resample(MODIS_Red_ag, CO_C3Crop, method="bilinear")

##calculate NDVI removing NA and Negative values, multiplied by 10000
##NDVI <- NDVI(NIRstack=MODIS_NIR_rs, REDstack=MODIS_Red_rs,
##=-1000, scalefactor=10000, nlayers=12, filename="NDVI")

griffithdan/grassmap documentation built on May 17, 2019, 8:37 a.m.