我试图计算100,000个字符串向量中每个字符串的非字母数字字符数。我发现我当前的实现速度比我想要的慢。
我当前的实现使用purrr::map()
映射一个自定义函数,该函数在向量中的每个字符串上使用stringr
包。
library(dplyr)
library(stringr)
library(purrr)
# custom function that accepts string input and counts the number
# of non-alphanum characters
count_non_alnum <- function(x) {
stringr::str_detect(x, "[^[:alnum:] ]") %>% sum()
}
# character vector of length 100K
vec <- rep("Hello. World.", 100000)
# tokenize individual characters for each string
vec_tokens <- purrr::map(vec, function(x) {
stringr::str_split(x, "") %>% unlist()
})
# count non-alphanum characters
purrr::map(vec_tokens, count_non_alnum)
# Time difference of 1.048214 mins
sessionInfo()
# R version 3.4.3 (2017-11-30)
# Platform: x86_64-w64-mingw32/x64 (64-bit)
# Running under: Windows 7 x64 (build 7601) Service Pack 1
我的模拟一直需要大约1分钟才能完成。我没有太多的期望基础,但我希望有更快的选择。我对替代R包或接口(例如网状,Rcpp)持开放态度。
基本R功能要快得多。这是一个sum/grepl
解决方案和调用这两个函数的4种不同方式。
library(microbenchmark)
library(ggplot2)
library(dplyr)
library(stringr)
library(purrr)
# custom function that accepts string input and counts the number
# of non-alphanum characters
count_non_alnum <- function(x) {
stringr::str_detect(x, "[^[:alnum:] ]") %>% sum()
}
count_non_alnum2 <- function(x) {
sum(grepl("[^[:alnum:] ]", x))
}
# character vector of length 100K
vec <- rep("Hello. World.", 100)
# tokenize individual characters for each string
vec_tokens <- purrr::map(vec, function(x) {
stringr::str_split(x, "") %>% unlist()
})
# count non-alphanum characters
mb <- microbenchmark(
Danny_purrr = purrr::map(vec_tokens, count_non_alnum),
Rui_purrr = purrr::map(vec_tokens, count_non_alnum2),
Danny_base = sapply(vec_tokens, count_non_alnum),
Rui_base = sapply(vec_tokens, count_non_alnum2),
unit = "relative"
)
mb
#Unit: relative
# expr min lq mean median uq max neval cld
# Danny_purrr 58.508234 56.440147 52.854162 53.890724 53.464640 25.855456 100 c
# Rui_purrr 1.026362 1.021998 1.011265 1.025648 1.025087 1.558001 100 a
# Danny_base 58.643098 56.398330 52.491478 53.857666 52.821759 27.981780 100 b
# Rui_base 1.000000 1.000000 1.000000 1.000000 1.000000 1.000000 100 a
autoplot(mb)