Transform formation fractions as in the first published mkin version

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This transformation was used originally in mkin, in order to implement a -constraint for the sum of formation fractions to be smaller than 1. It was -later replaced by the ilr transformation because the ilr transformed -fractions can assumed to follow normal distribution. As the ilr -transformation is not available in RxODE and can therefore not be used in -the nlmixr modelling language, the original transformation is currently used -for translating mkin models with formation fractions to more than one target -compartment for fitting with nlmixr in nlmixr_model. However, this -implementation cannot be used there, as it is not accessible from RxODE.

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tffm0(ff)
-
-invtffm0(ff_trans)

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Arguments

ff: Vector of untransformed formation fractions. The sum -must be smaller or equal to one
ff_trans: Vector of transformed formation fractions that can be -restricted to the interval from 0 to 1

Value

A vector of the transformed formation fractions -A vector of backtransformed formation fractions for natural use in degradation models

Details

If the transformed formation fractions are restricted to the interval -between 0 and 1, the sum of backtransformed values is restricted -to this interval.

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Examples

ff_example <- c(
-  0.10983681, 0.09035905, 0.08399383
-)
-ff_example_trans <- tffm0(ff_example)
-invtffm0(ff_example_trans)
-#> [1] 0.10983681 0.09035905 0.08399383
-

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