Occasionally, I would encounter a problem in R where I want to split a string in a character columns with the same separator. However, there’s is no function in R that is capable of doing that, and the strsplit function always return a list which I have to unlist it.
So today, I finally typed up a Rcpp function to ease my work and the code is as followed.
The function takes three inputs:
Test the code:
library(Rcpp)
sourceCpp('~/scripts/R/Rcpp/string_split.cpp')
testVector <- rep('I~am~a~boy',10)
for (i in 1:4){
print(string_split(testVector,'~',i))
}
## [1] "I" "I" "I" "I" "I" "I" "I" "I" "I" "I"
## [1] "am" "am" "am" "am" "am" "am" "am" "am" "am" "am"
## [1] "a" "a" "a" "a" "a" "a" "a" "a" "a" "a"
## [1] "boy" "boy" "boy" "boy" "boy" "boy" "boy" "boy" "boy" "boy"
Benchmarking:
library(rbenchmark)
library(ggplot2)
## Loading required package: methods
r_string_split <- function(x){
sapply(x,function(y) unlist(strsplit(x,'~'))[2])
}
bm <- benchmark(string_split(testVector,'~',2),r_string_split(testVector))
bm
## test replications elapsed relative user.self
## 2 r_string_split(testVector) 100 0.050 25 0.049
## 1 string_split(testVector, "~", 2) 100 0.002 1 0.001
## sys.self user.child sys.child
## 2 0 0 0
## 1 0 0 0
ggplot(data = bm,aes(x = test, y = relative)) +
geom_bar(stat='identity') +
theme(axis.text.x = element_text(angle=90,
hjust = 1,
vjust = 0.5))+
labs(y = 'relative speed',title = 'benchmarking result')
The c++ function is ~25x faster.
