R: Get variable names

variables {validate} | R Documentation

## Get variable names

### Description

Generic function that extracts names of variables ocurring in R objects.

### Usage

    variables(x, ...)

    ## S4 method for signature 'rule'
    variables(x, ...)

    ## S4 method for signature 'list'
    variables(x, ...)

    ## S4 method for signature 'data.frame'
    variables(x, ...)

    ## S4 method for signature 'environment'
    variables(x, ...)

    ## S4 method for signature 'expressionset'
    variables(x, as = c("vector", "matrix", "list"),
      dummy = FALSE, ...)

### Arguments

`x` | An R object
`...` | Arguments to be passed to other methods.
`as` | how to return variables: `'vector'` Return the uniqe vector of variables occurring in `x`. `'matrix'` Return a boolean matrix, each row representing a rule, each column representing a variable. `'list'` Return a named `list`, each entry containing a character vector with variable names.
`dummy` | Also retrieve transient variables set with the `:=` operator.

### Methods (by class)

- `rule`: Retrieve unique variable names

- `list`: Alias to `names.list`

- `data.frame`: Alias to `names.data.frame`

- `environment`: Alias to `ls`

- `expressionset`: Variables occuring in `x` either as a single list, or per rule.

### See Also

Other expressionset-methods: `as.data.frame,expressionset-method`, `as.data.frame`, `created`, `description`, `label`, `meta`, `names<-,rule,character-method`, `origin`, `plot,validator-method`, `summary`, `voptions`

Other expressionset-methods: `as.data.frame,expressionset-method`, `as.data.frame`, `created`, `description`, `label`, `meta`, `names<-,rule,character-method`, `origin`, `plot,validator-method`, `summary`, `voptions`

### Examples

    v <- validator(
      root = y := sqrt(x)
     , average = mean(x) > 3
     , sum = x + y == z
    )
    variables(v)
    variables(v,dummy=TRUE)
    variables(v,matrix=TRUE)
    variables(v,matrix=TRUE,dummy=TRUE)

[Package validate version 0.2.6 Index]