R: Interpolate values into an expression.

interp {lazyeval} | R Documentation

## Interpolate values into an expression.

### Description

This is useful if you want to build an expression up from a mixture of constants and variables.

### Usage

    interp(`_obj`, ..., .values)

### Arguments

`_obj` | An object to modify: can be a call, name, formula, `lazy`, or a string.
`..., .values` | Either individual name-value pairs, or a list (or environment) of values.

### Examples

    # Interp works with formulas, lazy objects, quoted calls and strings
    interp(~ x + y, x = 10)
    interp(lazy(x + y), x = 10)
    interp(quote(x + y), x = 10)
    interp("x + y", x = 10)

    # Use as.name if you have a character string that gives a
    # variable name
    interp(~ mean(var), var = as.name("mpg"))
    # or supply the quoted name directly
    interp(~ mean(var), var = quote(mpg))

    # Or a function!
    interp(~ f(a, b), f = as.name("+"))
    # Remember every action in R is a function call:
    # http://adv-r.had.co.nz/Functions.html#all-calls

    # If you've built up a list of values through some other
    # mechanism, use .values
    interp(~ x + y, .values = list(x = 10))

    # You can also interpolate variables defined in the current
    # environment, but this is a little risky.
    y <- 10
    interp(~ x + y, .values = environment())

[Package lazyeval version 0.2.1 Index]