R: Unevaluated Expressions

expression {base} | R Documentation

## Unevaluated Expressions

### Description

Creates or tests for objects of mode `"expression"`.

### Usage

    expression(...)

    is.expression(x)
    as.expression(x, ...)

### Arguments

`...` | valid R expressions.
`x` | an arbitrary R object.

### Value

`expression` returns a vector of mode `"expression"` containing its arguments as unevaluated “calls”.
`is.expression` returns `TRUE` if `expr` is an expression object and `FALSE` otherwise.
`as.expression` attempts to coerce its argument into an expression object.

### References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

### See Also

`call`, `eval`, `function`. Further, `text` and `legend` for plotting math expressions.

### Examples

    length(ex1 <- expression(1+ 0:9))# 1
    ex1
    eval(ex1)# 1:10

    length(ex3 <- expression(u,v, 1+ 0:9))# 3
    mode(ex3 [3]) # expression
    mode(ex3[[3]])# call
    rm(ex3)

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