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Integrate spectral irradiance with optional weighting

Source: R/spectral_integration.R
spectral_integration.Rd

Integrates over a given spectrum, optionally over only a portion of the spectrum, optionally with a weighing function. Can be used to calculate spectral contributions in certain wavelength ranges, or to calculate (alphaopically equivalent daylight) illuminance.

Usage

spectral_integration(
  spectrum,
  wavelength.range = NULL,
  action.spectrum = NULL,
  general.weight = 1
)

Arguments

spectrum

Tibble with spectral data (1st col: wavelength, 2nd col: SPD values)

wavelength.range

Optional integration bounds (length-2 numeric)

action.spectrum

Either:

  • Tibble with wavelength and weighting columns

  • Name of built-in spectrum: "photopic", "melanopic", "rhodopic", "l_cone_opic", "m_cone_opic", "s_cone_opic"

general.weight

Scalar multiplier or "auto" for built-in efficacies

Value

Numeric integrated value

Details

The function uses trapezoidal integration and recognizes differing step-widths in the spectrum. If an action spectrum is used, values of the action spectrum at the spectral wavelenghts are interpolated with stats::approx().

The used efficacies for for the auto-weighting are:

  • photopic: 683.0015478

  • melanopic: 1/0.0013262

  • rhodopic: 1/0.0014497

  • l_cone_opic: 1/0.0016289

  • m_cone_opic: 1/0.0014558

  • s_cone_opic: 1/0.0008173

This requires input values in W/(m^2) for the spectrum. If it is provided in other units, the result has to be rescaled afterwards.

See also

Other Spectrum: normalize_counts(), spectral_reconstruction()

Examples

# creating an equal energy spectrum of value 1
spd <- data.frame(wl = 380:780, values = 1)

#integrating over the full spectrum
spectral_integration(spd)
#> [1] 400

#integrating over wavelengths 400-500 nm
spectral_integration(spd, wavelength.range = c(400, 500))
#> [1] 100

#calculating the photopic illuminance of an equal energy spectrum with 1 W/(m^2*nm)
spectral_integration(spd, action.spectrum = "photopic", general.weight = "auto")
#> [1] 72983.09

#calculating the melanopic EDI of an equal energy spectrum with 1 W/(m^2*nm)
spectral_integration(spd, action.spectrum = "melanopic", general.weight = "auto")
#> [1] 66109.89

# Custom action spectrum
custom_act <- data.frame(wavelength = 400:700, weight = 0.5)
spectral_integration(spd, wavelength.range = c(400,700), 
                     action.spectrum = custom_act, general.weight = 2)
#> [1] 300
                     
#using a spectrum that is broader then the action spectrum will not change the
#output, as the action spectrum will use zeros beyond its range