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Pack rserve_client -- prolog/r/r_call.pl
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This module make R available to SWISH using the Rserve R package. The module r_serve.pl implements a SWI-Prolog wrapper around the Rserve C++ client to realise the communication with the R server.

The Prolog view at R is inspired by real from Nicos Angelopoulos.

It consists of the following two predicates:

  • Var <- Expression Assign the result of evaluating the given R Expression to Var. Var can be a Prolog variable or an R expression.
  • <- Expression Evaluate expression, discarding the result. Possible console output is captured.

In addition, the quasi quotation r is defined. The quasi quotation takes Prolog variables as arguments and an R expression as content. Arguments (Prolog variable names) that match R identifiers cause the temporary of an R variable with that name bound to the translated Prolog value. R quasi quotations can be used as isolated goals, as well as as right-hand arguments to <-/2 and <-/1. The example below calls the R plot() function on the given Prolog list.

?- numlist(1,10,Data),

Images created by the R session are transferred as SVG and sent to the SWISH console using pengine_output/1.

 r_call(+Fun, +Options)
Construct and possibly call an R function. Fun can be an atom or a compound, eg plot, or plot(width=3). The predicate also supports multiple output destinations. Options processed:
If false (default true), do not call the result.
Term is unified with the constructed call
Variable for the output
- This is a partial implementation of the corresponding real predicate.
 r_console(+Stream, ?Term)[multifile]
Hook console interaction. Currently only used for <-/1 to emit the captured output. In this cases, Stream is stdout and Term is a list of strings, each representing a line of output. The list can be empty. If the hook fails, maplist(writeln, Term) is called to write the output to current_output.
 r_execute(+Assignments, +Command, -Result) is det
Execute the R command Command after binding the variables in Assignments and unify the result with Result.
Assignments- is a list of Name=Value, where Name must be a valid R indentifier.
Command- is a string holding the R command to execute
 r(+Content, +Vars, +VarDict, -Goal) is det
Parse {|r(Arg,...||R-code|} into a the expression below. This expression may be passed to <-/2 and <-/1 as well as used directly as a goal, calling r_execute/3.
r_execute(Assignments, Command, Result)
See also
- https://cran.r-project.org/doc/manuals/r-release/R-lang.html#Parser
To be done
- Verify more of the R syntax.
 rserve:r_open_hook(+Name, -R)[multifile]
Called for lazy creation to the Rserve server. Connections are per-thread. The destination depends on settings:
Unix domain socket
If rserve:socket is defined and not empty, it is taken as the path to a Unix domain socket to connect to.
TCP/IP socket
Else, if rserve:port and rserve:host is defined, we connect to the indicated host and port.

After the connection is established, the session can be configured using the hook r_init_session/1. The default calls r_setup_graphics/2 to setup graphics output to send SVG files.

 r_init_session(+RConn) is semidet[multifile]
Multifile hook that is called after the Rserve server has handed us a new connection. If this hook fails, r_setup_graphics/2 is called to setup capturing graphics as SVG files.
 r_setup_graphics(+Rconn, +Format) is det
Setup graphics output using files. Currently only supports Format = svg.
Hook to display images.
Images- is a list of images. Each image is of the form Format(String), where Format is the file extension. Currently only uses svg. If not defined, print_message/2 is called with the term r_images(Images).

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 <-(Arg1, Arg2)