Passing data from R to WebPPL

Data can be passed directly from R to WebPPL as in:

my_model <- "
var model = function () {
 var p = uniform(0, 1)
 var scores = map( function(d) {
 	return Binomial({n:4, p:p}).score(d)
 }, myDF)
 return scores
}
model()
"

webppl(my_model,
	   data = df,
	   data_var = "myDF")

In this example, myDF is not defined inside the WebPPL program, but is passed into it from R, using data = df. The argument data_var tells WebPPL what the data should be called.

Structure of data when passing

The standard case we consider is passing an R data frame to WebPPL.

If myDF looks like this in R:

Participant	Condition	Response
1	A	0.4
1	B	0.8
2	A	0.2

It will exist in WebPPL as a list of js objects e.g.

[
  { participant: 0, condition: "A", response: 0.4 },
  { participant: 0, condition: "B", response: 0.8 },
  { participant: 1, condition: "A", response: 0.2 },
  ...
]

Data gets passed via the jsonlite package using toJSON. Other objects can be passed. For example, if a list in R is passed, it will be appear as

> toJSON(list(a = 5, b= 3))
{"a":[5],"b":[3]} 

Contrast that with passing a data.frame

> toJSON(data.frame(a = 5, b = 3))
[{"a":5,"b":3}]