dex: Calculate expression for derivative calculations.

Description Usage Arguments Details Value Author(s) Examples

View source: R/derivs.R

Description

Converts input to an expression suitable for use in nlsDeriv and related functions.

Usage

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dex(x, do_substitute = NA, verbose = FALSE)

Arguments

x

An expression represented in a variety of ways. See Details.

do_substitute

Whether to use the expression passed as x, or to evaluate it and use its value.

verbose

Print messages describing the process.

Details

If do_substitute is NA, the following rules are used:

  1. An attempt is made to evaluate x. If that fails, the expression is used.

  2. If the evaluation succeeds and the value is a character vector, it is parsed.

  3. If the value is not a character vector and the expression is a single name, the value is used.

  4. Otherwise, the expression is used.

Once the expression is determined it may be simplified, by extracting the language object from a length-one expression vector, or the right-hand-side from a formula.

Normally a warning will be issued if x is a formula containing a left-hand side. To suppress this, wrap the formula in expression(), or pass it as a character string to be parsed.

Value

An expression or language object suitable as input to nlsDeriv and related functions.

Author(s)

Duncan Murdoch

Examples

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aa <- dex(~ x^2)
aa
str(aa)
bb <- dex(expression(x^2))
bb
str(bb)
cc <- dex("x^2")
cc
str(cc)

nlsr documentation built on Aug. 20, 2021, 9:08 a.m.