The stdvectors 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.
The package is available on CRAN : https://cran.r-project.org/package=stdvectors
- Create a vector by adding elements one by one :
sv <- stdvectorCreate(type='integer')
for(i in 1:10){
# yes we're modify the vector in-place !
stdvectorPushBack(sv,i)
}- Turn into an R vector
v <- stdvectorToVector(sv)- Tested on :
R: 3.3.2 64bit
OS: Window 10
CPU: i5 6600K @3.5 Ghz
RAM: 16 GB
# Note: do not increase this too much, otherwise the first test will take ages!
n <- 150000
# R vector (concatenation)
tm1 <- system.time({
v <- integer()
for(i in 1:n){
v[i] <- i
}
}
)
# R vector (pre-allocation -> unfair test since the assumption is not knowing the size in advance)
tm2 <- system.time({
v <- rep.int(NA_integer_,n)
for(i in 1:n){
v[i] <- i
}
}
)
# stdvector
tm3 <- system.time({
sv <- stdvectorCreate(type='integer')
for(i in 1:n){
stdvectorPushBack(sv,i)
}
v <- stdvectorToVector(sv)
}
)
> tm1
user system elapsed
10.84 0.00 10.84
> tm2
user system elapsed
0.13 0.00 0.13
> tm3
user system elapsed
0.18 0.00 0.19 As you can see the difference is big, and it becomes bigger and bigger as the number of elements grows.
GPL (>= 2)