R: Energy:energy ratio

e_ratio {photobiology} | R Documentation

## Energy:energy ratio

### Description

This function returns the photon ratio for a given pair of wavebands of a light source spectrum.

### Usage

    e_ratio(spct, w.band.num, w.band.denom, wb.trim, use.cached.mult, use.hinges,
      ...)

    ## Default S3 method:
    e_ratio(spct, w.band.num, w.band.denom, wb.trim,
      use.cached.mult, use.hinges, ...)

    ## S3 method for class 'source_spct'
    e_ratio(spct, w.band.num = NULL, w.band.denom = NULL,
      wb.trim = getOption("photobiology.waveband.trim", default = TRUE),
      use.cached.mult = FALSE,
      use.hinges = getOption("photobiology.use.hinges"), ...)

    ## S3 method for class 'source_mspct'
    e_ratio(spct, w.band.num = NULL, w.band.denom = NULL,
      wb.trim = getOption("photobiology.waveband.trim", default = TRUE),
      use.cached.mult = FALSE,
      use.hinges = getOption("photobiology.use.hinges"), ..., attr2tb = NULL,
      idx = !is.null(names(spct)), .parallel = FALSE, .paropts = NULL)

### Arguments

`spct` | source_spct
`w.band.num` | waveband object or a list of waveband objects used to compute the numerator(s) of the ratio(s).
`w.band.denom` | waveband object or a list of waveband objects used to compute the denominator(s) of the ratio(s).
`wb.trim` | logical if TRUE wavebands crossing spectral data boundaries are trimmed, if FALSE, they are discarded
`use.cached.mult` | logical Flag telling whether multiplier values should be cached between calls.
`use.hinges` | logical Flag indicating whether to insert "hinges" into the spectral data before integration so as to reduce interpolation errors at the boundaries of the wavebands.
`...` | other arguments (possibly used by derived methods).
`attr2tb` | character vector, see `add_attr2tb` for the syntax for `attr2tb` passed as is to formal parameter `col.names`.
`idx` | logical whether to add a column with the names of the elements of spct
`.parallel` | if TRUE, apply function in parallel, using parallel backend provided by foreach
`.paropts` | a list of additional options passed into the foreach function when parallel computation is enabled. This is important if (for example) your code relies on external data or packages: use the .export and .packages arguments to supply them so that all cluster nodes have the correct environment set up for computing.

### Value

In the case of methods for individual spectra, a `numeric` vector of adimensional values giving a energy ratio between integrated energy irradiances for pairs of wavebands, with name attribute set to the name of the wavebands unless a named list of wavebands is supplied in which case the names of the list elements are used, with "(e:e)" appended. A `data.frame` in the case of collections of spectra, containing one column for each ratio definition, an index column with the names of the spectra, and optionally additional columns with metadata values retrieved from the attributes of the member spectra.

Ratio definitions are "assembled" from the arguments passed to `w.band.num` and `w.band.denom`. If both arguments are of equal length, then the wavebands are paired to obtain as many ratios as the number of wavebands in each list. Recycling for wavebands takes place when the number of denominator and numerator wavebands differ.

### Methods (by class)

- `default`: Default for generic function

- `source_spct`: Method for `source_spct` objects

- `source_mspct`: Calculates energy:energy ratio from a `source_mspct` object.

### Note

Recycling for wavebands takes place when the number of denominator and denominator wavebands differ. The last two parameters control speed optimizations. The defaults should be suitable in most cases. If you will use repeatedly the same SWFs on many spectra measured at exactly the same wavelengths you may obtain some speed up by setting `use.cached.mult=TRUE`. However, be aware that you are responsible for ensuring that the wavelengths are the same in each call, as the only test done is for the length of the `w.length` vector.

### See Also

Other photon and energy ratio functions: `eq_ratio`, `q_ratio`, `qe_ratio`

### Examples

    e_ratio(sun.spct, new_waveband(400,500), new_waveband(400,700))

[Package photobiology version 0.9.21 Index]