dex | R Documentation |

Calculate expression for derivative calculations.
Mainly for internal use, `dex()`

converts
its input to an expression suitable for use
in `nlsDeriv`

and related functions.

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

`x` |
An expression represented in a variety of ways. See Details. |

`do_substitute` |
Whether to use the expression passed as |

`verbose` |
Print messages describing the process. |

If `do_substitute`

is `NA`

, the following
rules are used:

An attempt is made to evaluate

`x`

. If that fails, the expression is used.If the evaluation succeeds and the value is a character vector, it is parsed.

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

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.

An expression or language object suitable as input
to `nlsDeriv`

and related functions.

Duncan Murdoch

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

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