讀取數字日期值在「R」

Question

> D <- read.csv("sample1.csv", header = FALSE, sep = ",") 

> D 
     V1  V2  V3  V4 
1 20100316 109825 352120 239065 
2 20100317 108625 352020 239000 
3 20100318 109125 352324 241065 

> D[,1] 
[1] 20100316 20100317 20100318 

在上面的例子中我如何才能在D[,1]數據被讀取，data.frame和日期值存儲：2010-03-16，2010 -03-17，2010-03-18？我有很多這種格式的數據文件。

TIA，

Answer 1

dx = "20100316 20100317 20100318"  
# if your dates already exists as individual items of mode "character" 
# then obviously, skip this step 
dx2 = unlist(strsplit(dx, split=" ")) 

fnx = function(x){as.Date(x, format="%Y%m%d")} 

dx3 = fnx(dx2) 
dx3 
# returns: [1] "2010-03-16" "2010-03-17" "2010-03-18" 

class(dx3) 
# returns: [1] "Date"