#R#《The R Book》笔记

1)#把R的数据写到粘贴板中，可以复制到Excel

write.table(r_data,"clipboard",sep="\t",col.names=NA)

2)#集合的处理

> a <- c("a","b","c","d")
> b <- c("a","b","e","g") ##unoin,intersect,setdiff 
> union(a,b)
[1] "a" "b" "c" "d" "e" "g"
> intersect(a,b) [1] "a" "b"
> setdiff(a,b) [1] "c" "d"
> setdiff(b,a) [1] "e" "g"
#Dates and Times
> Sys.time()
[1] "2013-03-27 09:23:50 CST"
> substr(as.character(Sys.time()),1,10)
[1] "2013-03-27"
> difftime("2013-1-2","2013-1-5")
Time difference of -3 days
> as.numeric(difftime("2013-1-2","2013-1-5"))
[1] -3