在 R 中将字符向量列表转换为数字的最快方法 [英] Fastest way to convert a list of character vectors to numeric in R

问题描述

在 R 中，将包含字符数字套件(作为字符向量)的列表转换为数字的最快方法是什么?

In R, what is the fastest way to convert a list containing suites of character numbers (as character vectors) into numeric?

使用以下虚拟数据:

set.seed(2)
N = 1e7
ncol = 10
myT = formatC(matrix(runif(N), ncol = ncol)) # A matrix converted to characters
# Each row is collapsed into a single suite of characters:
myT = apply(myT, 1, function(x) paste(x, collapse=' ') ) 
head(myT)

制作:

[1] "0.1849 0.855 0.8272 0.5403 0.3891 0.5184 0.7776 0.5533 0.1566 0.01591"  
[2] "0.7024 0.1008 0.9442 0.8582 0.3184 0.9289 0.9957 0.1311 0.2131 0.07355" 
[3] "0.5733 0.5493 0.3915 0.4423 0.8522 0.6042 0.9265 0.006878 0.7052 0.71"   
[... etc ...] 

我能做到

library(stringi) 
# In the actual dataset, the number of spaces between numbers may vary, hence "\\s+"
system.time(newT <- lapply(stri_split_regex(myT, "\\s+", omit_empty=T), as.numeric)) 
newT <- unlist(newT) # Final goal is to have a single vector of numbers

在我的 Intel Core i7 2.10GHz 和 64 位和 16GB 系统上(在 ubuntu 下):

On my Intel Core i7 2.10GHz with 64-bit and 16GB system (under ubuntu):

   user  system elapsed 
  3.748   0.008   3.757 

对于真实数据集(ncol=150 和 N~1e9)，这太长了.还有更好的选择吗?

With the real dataset (ncol=150 and N~1e9), this is way too long. Any better option?

推荐答案

这在我的系统上是两倍:

This is twice as fast on my system:

x <- paste(myT, collapse = "\n")
library(data.table)
DT <- fread(x)
newT2 <- c(t(DT))

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