问题
I wish to create a vector holding the position of elements from one vector in another vector. This is similar to the following questions:
Get the index of the values of one vector in another?
Is there an R function for finding the index of an element in a vector?
The match function in base R works in the simplest case, shown here:
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,2,3,4,5)
desired.output <- c(1,3,5,7,9)
match(b,a)
#[1] 1 3 5 7 9
However, match does not appear to work in more complex cases shown below. I might need a combination of which and match. In every case I am considering so far a value in b does not appear more often in b than in a. I need a base R solution.
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,2,2,3,4,5)
desired.output <- c(1,3,4,5,7,9)
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,2,2,3,4,4,5)
desired.output <- c(1,3,4,5,7,8,9)
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,2,2,3,4,4,5,5)
desired.output <- c(1,3,4,5,7,8,9,10)
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,1,2,2,3,4,4,5,5)
desired.output <- c(1,2,3,4,5,7,8,9,10)
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,1,2,2,3,3,4,4,5,5)
desired.output <- c(1,2,3,4,5,6,7,8,9,10)
回答1:
You are looking for pmatch:
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,2,3,4,5)
pmatch(b,a)
#[1] 1 3 5 7 9
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,2,2,3,4,5)
pmatch(b,a)
#[1] 1 3 4 5 7 9
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,2,2,3,4,4,5)
pmatch(b,a)
#[1] 1 3 4 5 7 8 9
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,2,2,3,4,4,5,5)
pmatch(b,a)
#[1] 1 3 4 5 7 8 9 10
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,1,2,2,3,4,4,5,5)
pmatch(b,a)
#[1] 1 2 3 4 5 7 8 9 10
a <- c(1,1,2,2,3,3,4,4,5,5)
b <- c(1,1,2,2,3,3,4,4,5,5)
pmatch(b,a)
# [1] 1 2 3 4 5 6 7 8 9 10
来源：https://stackoverflow.com/questions/65086390/position-of-elements-from-one-vector-in-another-vector-with-r