Calling R functions with keyword argumets that have attributes

[mbeltagy]

If I was to call R's stars function. It is easy to invoke it with

rprint(rcall(:stars,myDf))

However if I try to set the draw.segments=TRUE as I would in R. The following invocation fails

rprint(rcall(:stars,myDf,draw.segments=true))
ERROR: syntax: keyword argument is not a symbol: "draw.segments"

I saw nothing in the documentation to clarify how this might be handled.

[dmbates]

I don't think the example is reproducible so I will ask you to try

rprint(rcall(:stars,myDF;draw.segments=true))

to see if that works. In Julia named arguments are allowed only after the ; separator.

[simonbyrne]

actually the separator is only required for definitions, you don't need it for calling

[mbeltagy]

I tried it and it did not work. I got the same error

rprint(rcall(:stars,myDf;draw.segments=true))
ERROR: syntax: keyword argument is not a symbol: "draw.segments"

The trouble appears to be with draw.segments. Julia seems to be having trouble passing it along to R. In Julia, I have never come across keyword arguments with attributes as in R.

[simonbyrne]

@mbeltagy I don't yet have a good way to handle that case.

[randy3k]

It is one of the ways to mimic this, certainly not a good way.

eval(:(rcall(:stars,:mtcars,$(symbol("draw.symbol"))=true)))

It may be also of interest to implement a @rcall macro to handle non-standard keywords and lazy evaluation #42.

[mbeltagy]

It works!

 eval(:(rcall(:stars,:mtcars,$(symbol("draw.segments"))=true)))

The syntax is a bit cumbersome though. I look forward to an @rcall macro.

[simonbyrne]

A neat hack I once came across somewhere (I don't remember where). Define the following:

macro var_str(s)
    symbol(s)
end

then the following should work:

rprint(rcall(:stars,myDF;var"draw.segments"=true))

[simonbyrne]

I would be okay with incorporating something along these lines. Any suggestions for a good prefix? r, s, and v are all taken by various uses in Base (which, unfortunately, are the 3 most relevant in this case).

[simonbyrne]

I've added the above macro, so hopefully that is a reasonable solution.