Description Usage Arguments Details Value Note Source See Also Examples

View source: R/colorSpec.actinometric.R

Convert a radiometric **colorSpec** object to have
quantity that is actinometric (number of photons).
Test an object for whether it is actinometric.

1 2 3 4 5 | ```
## S3 method for class 'colorSpec'
actinometric( x, multiplier=1, warn=FALSE )
## S3 method for class 'colorSpec'
is.actinometric( x )
``` |

`x` |
a |

`multiplier` |
a scalar which is multiplied by the output, and intended for unit conversion |

`warn` |
if |

If the `quantity`

of `x`

does not start with `'energy'`

then the quantity is not radiometric and so `x`

is returned unchanged.
Otherwise `x`

is radiometric (energy-based), and must be converted.

If `type(x)`

is `'light'`

then
the most common radiometric energy unit is joule.

The conversion equation is:

* Q = E * λ * 10^6 / (N_A * h * c)*

wher *Q* is the photon count,
*E* is the energy of the photons,
*N_A* is Avogadro's constant,
*h* is Planck's constant, *c* is the speed of light,
and *λ* is the wavelength.
The output unit of photon count is
(*μ*mole of photons) = (*6.02214 * 10^{17}* photons).
If a different unit for `Q`

is desired,
then the output should be scaled appropriately.
For example, if the desired unit of photon count is exaphotons,
then set `multiplier=0.602214`

.

If the `quantity(x)`

is `'energy->electrical'`

,
then the most common radiometric unit of responsivity to light
is coulombs/joule (C/J) or amps/watt (A/W).
The conversion equation is:

* QE = R_e * ((h * c)/e) / λ *

where *QE* is the quantum efficiency,
*R_e* is the energy-based responsivity,
and *e* is the charge of an electron (in C).

If the unit of `x`

is not C/J,
then `multiplier`

should be set appropriately.

If the `quantity(x)`

is
`'energy->neural'`

or `'energy->action'`

,
the most common radiometric unit of energy is joule (J).

The conversion equation is:

* R_p = R_e * 10^{-6} * ( N_A * h * c) / λ *

where *R_p* is the photon-based responsivity,
and *R_e* is the energy-based responsivity,
The output unit of photon count is
(*μ*mole of photons) = (*6.02214 * 10^{17}* photons).
This essentially the reciprocal of the first conversion equation.

The argument `multiplier`

is applied to the right side of all the above
conversion equations.

`actinometric()`

returns a **colorSpec** object
with `quantity`

that is
actinometric (photon-based) and not radiometric (energy-based).
If `type(x)`

is a material type
(`'material'`

or `'responsivity.material'`

)
then `x`

is returned unchanged.

If `quantity(x)`

starts with `'photons'`

,
then `is.actinometric()`

returns `TRUE`

, and otherwise `FALSE`

.

To log the executed conversion equation,
execute `cs.options(loglevel='INFO')`

.

Wikipedia.
**Photon counting**.
http://en.wikipedia.org/wiki/Photon_counting

`quantity`

,
`type`

,
`cs.options`

,
`radiometric`

1 2 3 4 5 6 7 8 9 10 11 12 | ```
colSums( solar.irradiance ) # step size is 1nm, from 280 to 1000 nm. organized as a matrix
# AirMass.0 GlobalTilt AirMass.1.5
# 944.5458 740.3220 649.7749 # irradiance, watts*m^{-2}
colSums( actinometric(solar.irradiance) )
# AirMass.0 GlobalTilt AirMass.1.5
# 4886.920 3947.761 3522.149 # photon irradiance, (umoles of photons)*sec^{-1}*m^{-2}
colSums( actinometric(solar.irradiance,multiplier=0.602214) )
# AirMass.0 GlobalTilt AirMass.1.5
# 2942.972 2377.397 2121.088 # photon irradiance, exaphotons*sec^{-1}*m^{-2}
``` |

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