Function that converts transmittance (fraction) into \(\log_{10}\)-based absorbance (a.u.).
Usage
T2A(x, action, byref, clean, ...)
# Default S3 method
T2A(x, action = NULL, byref = FALSE, ...)
# S3 method for class 'numeric'
T2A(x, action = NULL, byref = FALSE, clean = TRUE, ...)
# S3 method for class 'filter_spct'
T2A(x, action = "add", byref = FALSE, clean = TRUE, strict.A = FALSE, ...)
# S3 method for class 'filter_mspct'
T2A(
x,
action = "add",
byref = FALSE,
clean = TRUE,
strict.A = TRUE,
...,
.parallel = FALSE,
.paropts = NULL
)
Arguments
- x
an R object.
- action
character Allowed values
"replace"
and"add"
.- byref
logical indicating if new object will be created by reference or by copy of
x
.- clean
logical replace off-boundary values before conversion
- ...
not used in current version
- strict.A
logical Attempt to compute a true internal absorbance even if
"total"
transmittance is stored inx
.- .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
A copy of x
with a column A
added and other columns
possibly deleted except for w.length
. If action = "replace"
,
in all cases, the additional columns are removed, even if no column needs
to be added.
Details
Absorbance, \(A\), is frequently used in chemistry as it is linearly related to the concentration of a solute dissolved in a solvent.
$$A = -\log_{10} \tau$$
where, \(A\) absorbance and \(\tau\) is internal transmittance. By
default, if total transmittance, \(T\), is stored in x
, the
returned value computed as
$$A = -\log_{10} T$$
is not strictly absorbance. In this case and in cases when the measured light attenuation is the result of scattering, or when part of measured light is re-emitted after absorption the use of attenuance is the IUPAC-recommended name for this quantity.
If strict.A = TRUE
is passed in the call and total
transmittance, \(T\), and total
reflectance, \(\rho\), are both available, absorbance is computed as:
$$A = -\log_{10} (T - \rho) / (1 - \rho)$$
where \(\rho\) can be either spectral total reflectance stored in x
as data or a single approximate Rfr.constant
value stored as part
of the metadata.
Methods (by class)
T2A(default)
: Default method for generic functionT2A(numeric)
: Method for numeric vectorsT2A(filter_spct)
: Method for filter spectraT2A(filter_mspct)
: Method for collections of filter spectra
See also
Other quantity conversion functions:
A2T()
,
Afr2T()
,
T2Afr()
,
any2T()
,
as_quantum()
,
e2q()
,
e2qmol_multipliers()
,
e2quantum_multipliers()
,
q2e()