RcppParams {Rcpp}R Documentation

C++ class for receiving (scalar) parameters from R

Description

RcppParams is a C++ class defined in Rcpp.h that receive any number of scalar parameters of types in a single named list object from R through the .Call() function.

The parameters can be of different types that are limited to the R types numeric, integer, character, logical or Date. These types are mapped into, respectively, the corresponding C++ types double, int, string, bool and Date (a custom class defined by Rcpp.

Usage

  val <- RcppParamsExample(params) 

Arguments

params A heterogeneous list specifying method (string), tolerance (double), maxIter (int) and startDate (Date in R, RcppDate in C++).

Details

Usage of RcppParams from R via .Call() is as follows:

  # an R example passing one type of each class to a function
  # someFunction in package somePackage
  val <- .Call("someFunction",
               list(pie=3.1415, magicanswer=42, sometext="foo",
                    yesno=true, today=Sys.date()),
                    PACKAGE="somePackage")

At the C++ level, the corresponding code to assign these parameter to C++ objects is

  SEXP someFunction(SEXP params) {
    RcppParams par(params);
    double p   = RcppParams.getDoubleValue("pie");
    int magic  = RcppParams.getIntValue("magicanswer");
    string txt = RcppParams.getStringValue("sometext");
    bool yn    = RcppParams.getBoolValue("yesno");
    RcppDate d = RcppParams.getDateValue("today");
    // some calculations ...
    // some return values ...
  }
As the lookup is driven by the names givem at the R level, order is not important. It is however important that the types match. Errors are typically caught and an exception is thrown.

The class member function checkNames can be used to verify that the SEXP object passed to the function contains a given set of named object.

Value

RcppExample returns a list containing:

method string input paramter
tolerance double input paramter
maxIter int input parameter
startDate Date type with starting date
params input parameter list (this is redundant because we returned the input parameters above)

Author(s)

Dominick Samperi wrote most of Rcpp during 2005 and 2006. Dirk Eddelbuettel made some additions, and became maintainer in 2008.

See Also

RcppExample, the vignette “RcppAPI”.

Examples


# set up some value
params <- list(method='BFGS',
               tolerance=1.0e-5,
               maxIter=100,
               startDate=as.Date('2006-7-15'))

# call the underlying  C++ function
result <- RcppParamsExample(params)

# inspect returned object
result


[Package Rcpp version 0.6.5 Index]