Interface with froth from R — froth-RInterface • froth

Methods to communicate with the froth environment without dropping into a REPL.

Usage

froth.RPush(object)
froth.RPop(nobj=1L)
froth.RDefine(name, fun, nargs)

Arguments

object: An R object to push to the froth stack
nobj: Number of objects to pop from the froth stack
name: Froth name for fun; see Examples
fun: An R function to define within froth
nargs: Number of arguments expected for fun

Details

These functions allow interaction with the froth stack from R. froth.RPush and froth.RPop allow push/pop operations on the froth stack. These operations are called from R, so pushing any R object is supported.

Some functions are easier to define using R than froth. froth.RDefine creates a froth function wrapper to call a specified R function, and then builds it into the froth environment. This makes using functions like rnorm within froth easier; see below for an illustrative example.

Functions defined with froth.RDefine expect their arguments to be popped directly off the froth stack, with the top of the stack corresponding to the last argument of the function.

Value

froth.RPop returns a list with the top nobj elements of the stack.

froth.RPush and froth.RDefine invisibly return an integer corresponding to the status of the operation. 0 indicates normal completion.

Author

Aidan Lakshman ahl27@pitt.edu

Note

Functions defined with froth.RDefine will not be saved using saveFrothSession.

Examples

## Example of calling rnorm in froth

## rnorm expects 3 arguments: rnorm(n, mean, sd)
froth.RDefine(name='R_rnorm', fun=rnorm, nargs=3L)

## Now we can call rnorm from froth using the 'R_rnorm' word.
## Note that the arguments are expected on the stack
## such that the top of the stack is `sd`,
## the second is `mean`, and the third is `n`.

## n
froth.RPush(5)

## mean
froth.RPush(0.0)

## sd
froth.RPush(1.0)

## running the function
## note this will push the results back onto the stack
froth.parse("R_rnorm")

## we can get the result with froth.RPop
froth.RPop(5L)
#> [[1]]
#> [1] -1.400044
#> 
#> [[2]]
#> [1] 0.2553171
#> 
#> [[3]]
#> [1] -2.437264
#> 
#> [[4]]
#> [1] -0.005571287
#> 
#> [[5]]
#> [1] 0.6215527
#> 

## As a oneliner: (doesn't return the values)
froth.parse("5 0 1 R_rnorm .s")
#> [[1]]
#> [1] 1.148412
#> 
#> [[2]]
#> [1] -1.821818
#> 
#> [[3]]
#> [1] -0.2473253
#> 
#> [[4]]
#> [1] -0.2441996
#> 
#> [[5]]
#> [1] -0.2827054
#> 
#> [[6]]
#> NULL
#>