R：匹配另一个向量中的向量作为整体

Question

Is there an easy, straightforward way (possibly a builtin function) that could match one vector as a whole in another vector? Example:

target <- c(1,2,3)
A <- c(4,5,6,1,2,3)
B <- c(4,5,6,3,2,1)

my_match(target, A) # TRUE
my_match(target, B) # FALSE

I tried %in% , match and pmatch but these won't give the desired result. For example, both target %in% A and target %in% B will give the result [1] TRUE TRUE TRUE , which is not what I want.

Answer 1

Here another version

multi_match=function(target,A) {
  lA=length(A)
  lt=length(target)
  if (lt>lA) return(FALSE)
  any(colSums(sapply(1:(lA-lt+1),function(i) A[i:(i+lt-1)])==target)==lt)
}

Let's try it with some data

target <- c(1,2,3)
A <- c(4,5,6,1,2,3,1,2,3,1,3)
B <- c(4,5,6,3,2,1)

multi_match(target,A)
#TRUE

multi_match(target,B)
#FALSE

#"wrong" input order - trivially no match
multi_match(A,target)
#FALSE

And an extension of the multi_match function above to multi_which .

multi_which=function(target,A) {
  lA=length(A)
  lt=length(target)
  if (lt>lA) return(integer(0))
  which(colSums(sapply(1:(lA-lt+1),function(i) A[i:(i+lt-1)])==target)==lt)
}


multi_which(target,A)
#[1] 4 7

multi_which(target,B)
#integer(0)

#"wrong" input order - trivially no match
multi_which(A,target)
#integer(0)

Answer 2

Try:

grepl(paste(target,collapse=","),paste(A,collapse=","))
grepl(paste(target,collapse=","),paste(B,collapse=","))

This concatenates the vectors into strings and looks for a substring in the second argument that matches the first.

You could put this into a function that returns true or false:

my_match <- function(x,y,dlm=",") grepl(paste(x,collapse=dlm),paste(y,collapse=dlm))

my_match(target,A)
[1] TRUE
my_match(target,B)
[1] FALSE

Answer 3

One possible way is to use match and check if resulting sequence is rising

all(diff(match(target, A)) == 1) && length(match(target, A)) == length(target)

Or as a function

> exact_match <- function(p, x) all(diff(match(p, x)) == 1) && length(match(p, x)) == length(p)
> exact_match(target,A)
[1] TRUE
> exact_match(target,B)
[1] FALSE