r - 在 R 中将数字转换为字符的最快方法

Question

我需要将数字向量转换为 R 中的字符。据我所知，有不同的方法(见下文)。

似乎最快的方法是 sprintf 和 gettextf。

set.seed(1)
a <- round(runif(100000), 2)
system.time(b1 <- as.character(a))
   user  system elapsed 
  0.108   0.000   0.105 
system.time(b2 <- formatC(a))
   user  system elapsed 
  0.052   0.000   0.052 
system.time(b3 <- sprintf('%.2f', a))
   user  system elapsed 
  0.044   0.000   0.046 
system.time(b4 <- gettextf('%.2f', a))
   user  system elapsed 
  0.048   0.000   0.046 
system.time(b5 <- paste0('', a))
   user  system elapsed 
  0.124   0.000   0.129 

是否有其他方法将数字转换为 R 中的字符？感谢您的任何建议。

Answer 1

其实好像是formatC出来更快:

library(microbenchmark)
a <- round(runif(100000), 2)
microbenchmark(
  as.character(a), 
  formatC(a), 
  format(a), 
  sprintf('%.2f', a), 
  gettextf('%.2f', a), 
  paste0('', a)
)

输出:

Unit: milliseconds
                expr      min       lq     mean   median       uq       max neval
     as.character(a) 69.58868 70.74803 71.98464 71.41442 72.92168  82.21936   100
          formatC(a) 33.35502 36.29623 38.83611 37.60454 39.27079  72.92176   100
           format(a) 55.98344 56.78744 58.00442 57.64804 58.83614  66.15601   100
  sprintf("%.2f", a) 46.54285 47.40126 48.53067 48.10791 49.12717  65.26819   100
 gettextf("%.2f", a) 46.74888 47.81214 49.23166 48.60025 49.16692  84.90208   100
       paste0("", a) 86.62459 88.67753 90.80720 89.86829 91.33774 125.51421   100

我的 sessionInfo :

R version 3.1.0 (2014-04-10)
Platform: x86_64-apple-darwin13.1.0 (64-bit)

locale:
[1] en_AU.UTF-8/en_AU.UTF-8/en_AU.UTF-8/C/en_AU.UTF-8/en_AU.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] microbenchmark_1.4-2

loaded via a namespace (and not attached):
 [1] colorspace_1.2-4 digest_0.6.4     ggplot2_1.0.0    grid_3.1.0       gtable_0.1.2     MASS_7.3-35     
 [7] munsell_0.4.2    plyr_1.8.1       proto_0.3-10     Rcpp_0.11.3      reshape2_1.4     scales_0.2.4    
[13] stringr_0.6.2    tools_3.1.0