R：如何计算1的数量并写入向量

Question

I have as signal-vector that looks like this:

a <- c(1,1,1,1,1,0,0,0,0,1,1,0,0,0,1,0,1,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,1,1,1)

I will count how often a 1 occurs in one raw and write that in to a vector b eg for vector a it should result in:

b
5,2,1,1,1,1,3

The reason is that i will plot a histogram that shows me the distribution of the length of the events. Maybe there is already a function in R that does exactly that? Otherwise with if-loop?

Cheers Greg

Answer 1

You could try rle (Note that these solutions are also from base R )

with(rle(a), lengths[!!values])
#[1] 5 2 1 1 1 1 3

Or

unname(table(cumsum(c(1,abs(diff(a)))))[c(TRUE, FALSE)])
#[1] 5 2 1 1 1 1 3

If the vector is not binary

with(rle(a), lengths[values==1])
#[1] 5 2 1 1 1 1 3

Or

unname(table(cumsum(c(1,abs(diff(a==1)))))[c(TRUE, FALSE)])

EDIT

If the vector starts with numbers other than 1 . For example 0 or 2 (as mentioned by @Ananda Mahto in the comments)

 a[1] <- 2
 a1 <- a[which(a==1)[1]:length(a)]
 unname(table(cumsum(c(1,abs(diff(a1==1)))))[c(TRUE, FALSE)])
 #[1] 4 2 1 1 1 1 3
 with(rle(a), lengths[values==1])
 #[1] 4 2 1 1 1 1 3

Or

with(rle(a == 1), lengths[values]) # from @Richard Scriven's comments

Answer 2

Shameless plug, but since you are only dealing with ones and zeroes, you could also use TrueSeq from my "SOfun" package ( only on GitHub ).

Here's what TrueSeq does:

library(SOfun)
TrueSeq(as.logical(a))
#  [1] 1 1 1 1 1 0 0 0 0 2 2 0 0 0 3 0 4 0 5 0 6 0 0 0 0 0 0 0 0 0 0 0 7 7 7

Keeping that in mind, you can just use tabulate on the output since that would discard the zeroes:

tabulate(TrueSeq(as.logical(a)))
# [1] 5 2 1 1 1 1 3

Answer 3

Another solution with base R :

count1<-strsplit(paste(a,collapse=""),"0")[[1]]
b<-nchar(count1[count1!=""])

> b
[1] 5 2 1 1 1 1 3