hsdar: normalized.ratio.index – R documentation

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normalized.ratio.index

Normalised ratio index

Description

Calculate normalised ratio index (nri) for a single given band combination or for all possible band combinations. Calculating nri is a frequently used method to standardize reflectance values and to find relationships between properties of the objects and their spectral data.

Usage

nri(x, b1, b2, recursive = FALSE, bywavelength = TRUE)

Arguments

`x`	List of class `Speclib` or of class `Nri` for print and as.matrix methods.
`b1`	Band 1 given as band number or wavelength.
`b2`	Band 2 given as band number or wavelength.
`recursive`	If TRUE indices for all possible band combinations are calculated. If FALSE, only a single nri for the given bands in `b1` and `b2` is calculated.
`bywavelength`	Flag to determine if b1 and b2 are band number (bywavelength = FALSE) or wavelength (bywavelength = TRUE) values.

Details

Function for nri performs the following calculation:

nri_{B1,~B2}=\frac{R_{B1}-R_{B2}}{R_{B1}-R_{B2}};

with R being reflectance values at wavelength B1 and B2, respectively.

If recursive = TRUE, all possible band combinations are calculated.

Value

If recursive = FALSE, a data frame with index values is returned. Otherwise result is an object of class Nri. See glm.nri for applying a generalised linear model to an array of normalised ratio indices.

Author(s)

Lukas Lehnert

References

Sims, D.A.; Gamon, J.A. (2002). Relationships between leaf pigment content and spectral reflectance across a wide range of species, leaf structures and developmental stages. Remote Sensing of Environment: 81/2, 337 - 354.

Thenkabail, P.S.; Smith, R.B.; Pauw, E.D. (2000). Hyperspectral vegetation indices and their relationships with agricultural crop characteristics. Remote Sensing of Environment: 71/2, 158 - 182.

Examples

data(spectral_data)

## Calculate NDVI
ndvi <- nri(spectral_data, b1=800, b2=680)

## Calculate all possible combinations for WorldView-2-8
spec_WV <- spectralResampling(spectral_data, "WorldView2-8",
                              response_function = FALSE)
nri_WV <- nri(spec_WV, recursive = TRUE)
nri_WV

hsdar

Manage, Analyse and Simulate Hyperspectral Data

v1.0.3

GPL

Authors

Lukas W. Lehnert [cre, aut] (<https://orcid.org/0000-0002-5229-2282>), Hanna Meyer [ctb], Joerg Bendix [ctb]

Initial release

2020-08-04