choose.trans: Functions to handle transformations of measuremnt results.
In MethComp: Analysis of Method Comparison studies

Description Usage Arguments Value Author(s) Examples

Choose a function and inverse based on a text string; check whether two functions actually are each others inverse.

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  choose.trans( tr )
  check.trans( trans, y, trans.tol = 1e-05 )

`tr`	A character string, or a list of two functions, they should be each other's inverse. Names of the list are ignored.
`trans`	A list of two functions, each other's inverse.
`y`	Vector of numerical values where the functions should be each other's inverse.
`trans.tol`	Numerical constant indication how precise the evaulation should be.

choose.trans returns a named list with two elements "trans" and "inv", both functions which are each other's inverse. This is intended to be stored as an attribute "Transform" with the resulting object and used in plotting and reporting. All results will be on the transformed scale. If the tr argument to choose.trans is a character constant, the appropriate named list of two functions will be generated. Possibilities are: "exp", "log", "logit", "pctlogit" (transforms percentages by the logit), "sqrt", "sq" (square), "cll" (complementary log-minus-log), "ll" (log-minus-log). If there is no match NULL is returned, which will correspond to no transformation.

check.trans returns nothing.

Bendix Carstensen, Steno Diabetes Center, http://www.biostat.ku.dk/~bxc.