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“粘贴”、“str\u c”、“str\u join”、“stri\u join”、“stri\u c”、“stri\u paste”之间的区别?

stringi stringr r

moodymudskipper · 技术社区 · 6 年前

所有这些看起来非常相似的功能之间有什么区别?

1 回复 | 直到 6 年前

moodymudskipper 6 年前

stri_join , stri_c ,和 stri_paste stringi 是纯化名
str_c 来自 stringr 只是 stringi::stri_join 带参数 ignore_null TRUE 虽然 strii::stri\u连接 设置为 FALSE 默认情况下。 stringr::str_join 是的不推荐使用的别名 结构

library(stringi)
identical(stri_join, stri_c)
# [1] TRUE
identical(stri_join, stri_paste)
# [1] TRUE

library(stringr)
str_c
# function (..., sep = "", collapse = NULL) 
# {
#   stri_c(..., sep = sep, collapse = collapse, ignore_null = TRUE)
# }
# <environment: namespace:stringr>

连续连接 非常类似于 base::paste 以下列举了一些不同之处:

1. sep = "" 默认情况下

paste0 默认情况下,但是 粘贴0 失去了它的 sep 争论。

identical(paste0("a","b")        , stri_join("a","b"))
# [1] TRUE
identical(paste("a","b")         , stri_join("a","b",sep=" "))
# [1] TRUE
identical(paste("a","b", sep="-"), stri_join("a","b", sep="-"))
# [1] TRUE

会表现得像在这里。

NA

如果粘贴到 不适用 使用 连续连接 ,结果是 不适用 paste 皈依者 不适用 到 "NA"

paste0(c("a","b"),c("c",NA))
# [1] "ac"  "bNA"
stri_join(c("a","b"),c("c",NA))
# [1] "ac" NA

会表现得像 连续连接 这里也是

0

当遇到长度0值时, character(0) 被退回,除非设置为 错误的 粘贴 这将转换长度 0 价值 ""

stri_join("a",NULL, "b")  
# [1] character(0)
stri_join("a",character(0), "b")  
# [1] character(0)

paste0("a",NULL, "b")
# [1] "ab"
stri_join("a",NULL, "b", ignore_null = TRUE)
# [1] "ab"
str_c("a",NULL, "b")
# [1] "ab"

paste("a",NULL, "b") # produces double space!
# [1] "a  b" 
stri_join("a",NULL, "b", ignore_null = TRUE, sep = " ")
# [1] "a b"
str_c("a",NULL, "b", sep = " ")
# [1] "a b"

4. 连续连接 更多警告

paste(c("a","b"),c("c","d","e"))
# [1] "a c" "b d" "a e"
paste("a","b", sep = c(" ","-"))
# [1] "a b"

stri_join(c("a","b"),c("c","d","e"), sep = " ")
# [1] "a c" "b d" "a e"
# Warning message:
#   In stri_join(c("a", "b"), c("c", "d", "e"), sep = " ") :
#   longer object length is not a multiple of shorter object length
stri_join("a","b", sep = c(" ","-"))
# [1] "a b"
# Warning message:
#   In stri_join("a", "b", sep = c(" ", "-")) :
#   argument `sep` should be one character string; taking the first one

速度更快

microbenchmark::microbenchmark(
  stringi = stri_join(rep("a",1000000),rep("b",1000),"c",sep=" "),
  base    = paste(rep("a",1000000),rep("b",1000),"c")
)

# Unit: milliseconds
#    expr       min       lq      mean    median       uq      max neval cld
# stringi  88.54199  93.4477  97.31161  95.17157  96.8879 131.9737   100  a 
# base    166.01024 169.7189 178.31065 171.30910 176.3055 215.5982   100   b