C++ Standard Library Vectors in R

Description

Allows the creation and manipulation of C++ std::vector's in R.

Details

This package allows the creation and manipulation of C++ std::vector's in R. std::vector's are dynamically allocated arrays, which are especially helpful when you need to fill a huge vector (e.g. in a loop) but you don't know the size in advance.

Author(s)

Marco Giuliano

Maintainer: Marco Giuliano <mgiuliano.mail@gmail.com>

References

cpp reference page : http://en.cppreference.com/w/

Examples

  # create a stdvector
  sv <- stdvectorCreate('integer')
  # add 100 values to it
  for(i in 1:100){
    # note that sv is modified in-place
    stdvectorPushBack(sv,i)
  }
  # get a normal R vector from the stdvector
  v <- stdvectorToVector(sv)

  ## Not run: 
  
    # check the time difference:
    # the first method takes around 2-3 s
    # the second method takes less than 0.1 s
    system.time({
        v <- integer()
        for(i in 1:100000){
          v[[length(v)+1]] <- i
        }
      }
    )
    system.time({
        v <- stdvectorCreate('integer')
        for(i in 1:100000){
          stdvectorPushBack(v,i)
        }
      }
    )

  
## End(Not run)

std::vector R wrapper

Description

Create and manipulate a C++ std:::vector in R.

Usage

stdvectorCreate(type = "double", reserve = 0L)
stdvectorPushBack(sdv, values)
stdvectorSize(sdv)
stdvectorClear(sdv)
stdvectorToVector(sdv)
stdvectorSubset(sdv,indexes)
stdvectorReplace(sdv,indexes,values)
stdvectorErase(sdv,indexFrom,indexTo)
stdvectorClone(sdv)
is.stdvector(x)
## S3 method for class 'stdvector'
print(x, ...)
## S3 method for class 'stdvector'
toString(x, ...)

Arguments

Details

• stdvectorCreate creates a stdvector object of the indicated type.

• stdvectorPushBack appends elements to an existing stdvector (see note for type='any').

• stdvectorSize returns the number of elements of an existing stdvector.

• stdvectorClear removes all the elements of an existing stdvector.

• stdvectorToVector turns an existing stdvector into an R vector of the type chosen when the stdvector has been created.

• stdvectorSubset subsets an existing stdvector returning an R vector with the values corresponding to the selected indexes.

• stdvectorReplace replace the elements at indexes positions with the values in values argument (see note for type='any').

• stdvectorErase remove the elements from indexFrom to indexTo positions.

• stdvectorClone create a deep copy of the stdvector object.

Value

• stdvectorCreate returns an object of class stdvector.

• stdvectorPushBack return NULL invisibly.

• stdvectorSize returns an integer equal to the size of the stdvector.

• stdvectorClear returns NULL invisibly.

• stdvectorToVector returns an R vector of the type chosen when the stdvector has been created (type='any' will return a list).

• stdvectorSubset returns an R vector (of the type chosen when the stdvector has been created, type='any' will return a list) with the values corresponding to the selected indexes.

• stdvectorReplace returns NULL invisibly.

• stdvectorErase returns NULL invisibly.

• stdvectorClone returns an object of class stdvector which is the copy of the passed object.

Note

stdvector

• stdvector objects are treated as references, so if you do sv2 <- sv1 and then you modify sv2 actually also sv1 will be modified. You need to do sv2 <- stdvectorClone(sv1) to actually create a copy.

• stdvectorPushBack in case of stdvector of type='any' will append the element passed in the argument values as a single new element of the vector, even if it's a list.

• stdvectorSubset indexes must be between 1 and the size of the stdvector.

• stdvectorReplace indexes and values must have the same length. In case of stdvector of type='any' will accept only indexes of length one.

References

See http://en.cppreference.com/w/cpp/container/vector

Examples

  # create a stdvector
  sv <- stdvectorCreate('integer')
  # add 100 values to it
  for(i in 1:100){
    # note that sv is modified in-place
    stdvectorPushBack(sv,i)
  }
  # get a normal R vector from the stdvector
  v <- stdvectorToVector(sv)