Find All Positions of All Matches of One Vector of Values in Second Vector

Find all positions of all matches of one vector of values in second vector

This should work:

which(hay %in% needles) # 2 3 5

Position of elements from one vector in another vector with R

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

How to find indices of element in one vector in other vector R

a <-  c('Q1', 'Q2', 'Q3')
b <- c('Q10', 'Q13', 'Q1', 'Q1', 'Q40', 'Q2', 'Q2', 'Q2')

which(b %in% a)

[1] 3 4 6 7 8

Get the index of the values of one vector in another?

Getting indexes of values is what match() is for.

 first = c( "a" , "c" , "b" )
 second = c( "c" , "b" , "a" )
 match(second, first)
 [1] 2 3 1

Finding All Positions for Multiple Elements in a Vector

This is one way to do it. First I get the indices at which x is either 8 or 9. Then we can verify that at those indices, x is indeed 8 and 9.

> inds <- which(x %in% c(8,9))
> inds
[1]  1  3  4 12 15 19
> x[inds]
[1] 8 9 9 8 9 8

Find matches of a vector of strings in another vector of strings

You can try pasting your "keywords" together and separate them with the pipe character (|) which will work like an "or", like this:

> articles[grepl(paste(keywords, collapse="|"), articles$text),]
  id                                                                         text
1  1     Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
2  2 tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
4  4    consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse

How to detect multiple strings in another vector of strings

You just need:

all_words %in% words

From help("%in%"):

%in% is a more intuitive interface as a binary operator, which returns
a logical vector indicating if there is a match or not for its left
operand.

Basically for each element in the first vector, it checks if there's a match in the left hand vector.

Get indexes of a vector of numbers in another vector

Using base R you could do the following:

v <- c(2,2,3,5,8,0,32,1,3,12,5,2,3,5,8,33,1)
x <- c(2,3,5,8)

idx <- which(v == x[1])
idx[sapply(idx, function(i) all(v[i:(i+(length(x)-1))] == x))]
# [1]  2 12

This tells you that the exact sequence appears twice, starting at positions 2 and 12 of your vector v.

It first checks the possible starting positions, i.e. where v equals the first value of x and then loops through these positions to check if the values after these positions also equal the other values of x.

Get indices of matches with a column in a second data.table

Using .EACHI and adding the resulting list column by reference.

dt2[ , res := dt1[ , i := .I][.SD, on = .(firstName), .(.(i)), by = .EACHI]$V1]
#    lid firstName res
# 1:   1     Maria  NA
# 2:   2       Jim 1,4
# 3:   3      Jack  NA
# 4:   4      Anne 3,5

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