分割矢量

Question

我有一個由「Y」和「N」組成的向量x。

> x 
[1] Y N N N N N N N N N N Y N N N N 

我想這個分成

> x1 
[1] Y N N N N N N N N N N 

和

> x2 
[1] Y N N N N 

這些矢量始終以 「Y」 開始之前下一個「採取一切 」N「 S Y」。如何做到這一點的建議？

Answer 1

有一定更好的方法，但是：

tst<-c("Y", "N", "N", "N", "N", "N", "N", "N", "N", "N", "N", "Y", "N", "N", "N", "N") 
starts<-which(tst=="Y") #where are the "Y" 
ends<-c(starts[-1]-1, length(tst)) #pos before each "Y"" 
lapply(seq_along(starts), function(i){tst[(starts[i]):(ends[i])]}) #parts from each start till each end 

Answer 2

摺疊成一個字符串，然後分裂的 「Y」 S。

x <- c("Y", "N", "N", "N", "N", "N", "N", "N", "N", "N", "N", "Y", "N", "N", "N", "N") 
y <- paste(x, collapse = "") 
z <- paste("Y", strsplit(pn, "Y")[[1]], sep = "")[-1] 
z 

或者使用運行長度編碼。

n <- rle(x)$lengths[c(FALSE, TRUE)] 
lapply(n, function(i) paste("Y", rep.int("N", i), sep = "", collapse = "")) 

（這會給你一個列表，而不是一個向量，使用unlist如果這不是你想要的。）

Answer 3

您可以使用cumsum和split的組合來做到這一點與單襯墊：

x <- c("Y","N","N","N","N","N","N","N","N","N","N","Y","N","N","N","N") 
v <- split(x,paste("x",cumsum(x=="Y"),sep=""))