Getting started

The RCall package is loaded via

julia> using RCall

This will initialize the R process in the background.

Several Ways to use RCall

RCall provides multiple ways to allow R interacting with Julia.

R REPL mode
@rput and @rget macros
R"" string macro
RCall API: reval, rcall and rcopy etc.

The R REPL mode allows real time switching between the Julia prompt and R prompt. Press $ to activate the R REPL mode and the R prompt will be shown. (Press backspace to leave R REPL mode in case you did not know.)

julia> foo = 1
1

R> x <- $foo

R> x
[1] 1

The R REPL mode supports variable substitution of Julia objects via the $ symbol. It is also possible to pass Julia expressions in the REPL mode.

R> x = $(rand(10))

R> sum(x)
[1] 5.097083

@rput and @rget macros

These macros transfer variables between R and Julia environments. The copied variable will have the same name as the original.

julia> z = 1
1

julia> @rput z
1

R> z
[1] 1

R> r = 2

julia> @rget r
2.0

julia> r
2.0

It is also possible to put and get multiple variables in one line.

julia> foo = 2
2

julia> bar = 4
4

julia> @rput foo bar
4

R> foo + bar
[1] 6

@R_str string macro

Another way to use RCall is the R"" string macro, it is especially useful in script files.

julia> R"rnorm(10)"
RCall.RObject{RCall.RealSxp}
 [1]  1.447699031 -0.150497135  1.358309791 -0.050428734  0.106393891
 [6] -0.132718273 -0.906666897 -0.001073414  0.608663094  0.224944697

This evaluates the expression inside the string in R, and returns the result as an RObject, which is a Julia wrapper type around an R object.

The R"" string macro supports variable substitution of Julia objects via the $ symbol, whenever it is not valid R syntax (i.e. when not directly following a symbol or completed expression such as aa$bb):

julia> x = randn(10)
10-element Array{Float64,1}:
  1.13664
  1.66621
  0.240552
 -0.134557
 -0.154693
 -0.430619
  0.588185
 -0.19285
 -1.09396
  0.357907

julia> R"t.test($x)"
RCall.RObject{RCall.VecSxp}

	One Sample t-test

data:  `#JL`$x
t = 0.79008, df = 9, p-value = 0.4498
alternative hypothesis: true mean is not equal to 0
95 percent confidence interval:
 -0.3694351  0.7659975
sample estimates:
mean of x
0.1982812

It is also possible to pass Julia expressions which are evaluated before being passed to R: these should be included in parentheses

julia> R"optim(0, $(x -> x-cos(x)), method='BFGS')"
RCall.RObject{RCall.VecSxp}
$par
[1] -1.56343

$value
[1] -1.570796

$counts
function gradient
      14       13

$convergence
[1] 0

$message
NULL

A large chunk of code could be quoted between triple string quotations

julia> y = 1
1

julia> R"""
       f <- function(x, y) x + y
       ret <- f(1, $y)
       """
RCall.RObject{RCall.RealSxp}
[1] 2

RCall API

The reval function evaluates any given input string as R code in the R environment. The returned result is an RObject object.

julia> jmtcars = reval("mtcars");

julia> names(jmtcars)
11-element Array{Symbol,1}:
 :mpg
 :cyl
 :disp
 :hp
 :drat
 :wt
 :qsec
 :vs
 :am
 :gear
 :carb

julia> jmtcars[:mpg]
RCall.RObject{RCall.RealSxp}
 [1] 21.0 21.0 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 17.8 16.4 17.3 15.2 10.4
[16] 10.4 14.7 32.4 30.4 33.9 21.5 15.5 15.2 13.3 19.2 27.3 26.0 30.4 15.8 19.7
[31] 15.0 21.4

julia> typeof(jmtcars)
RCall.RObject{RCall.VecSxp}

The rcall function is used to construct function calls.

julia> rcall(:dim, jmtcars)
RCall.RObject{RCall.IntSxp}
[1] 32 11

The arguments will be implicitly converted to RObject upon evaluation.

julia> rcall(:sum, Float64[1.0, 4.0, 6.0])
RCall.RObject{RCall.RealSxp}
[1] 11

The rcopy function converts RObjects to Julia objects. It uses a variety of heuristics to pick the most appropriate Julia type:

julia> rcopy(R"c(1)")
1.0

julia> rcopy(R"c(1, 2)")
2-element Array{Float64,1}:
 1.0
 2.0

julia> rcopy(R"list(1, 'zz')")
2-element Array{Any,1}:
 1.0
  "zz"

julia> rcopy(R"list(a=1, b='zz')")
DataStructures.OrderedDict{Symbol,Any} with 2 entries:
  :a => 1.0
  :b => "zz"

It is possible to force a specific conversion by passing the output type as the first argument:

julia> rcopy(Array{Int}, R"c(1,2)")
2-element Array{Int64,1}:
 1
 2

Converters and Constructors could also be used specifically to yield the desired type.

julia> convert(Array{Float64}, R"c(1,2)")
2-element Array{Float64,1}:
 1.0
 2.0

julia> Float64(R"1+3")
4.0