R: Find Vector in List of Vectors

R: find vector in list of vectors

If you just want to determine if the vector is in the list, try

Position(function(x) identical(x, state), final_states, nomatch = 0) > 0
# [1] TRUE

Position() basically works like match(), but on a list. If you set nomatch = 0 and check for Position > 0, you'll get a logical result telling you whether state is in final_states

R: Is a vector in a list of vectors

You can use

l = list(c(2,1), c(3,2), c(2,3))
x = c(3,2)
any(sapply(l, identical, x))

In R, find elements of a vector in a list using vectorization

we can do this, seems to be the fastest by far.

v1 <- c(1, 200, 4000)
L1 <- list(1:4, 1:4*100, 1:4*1000)

sequence(lengths(L1))[match(v1, unlist(L1))]
# [1] 1 2 4
sequence(lengths(L1))[which(unlist(L1) %in% v1)]
# [1] 1 2 4

---

library(microbenchmark)
library(tidyverse)

microbenchmark(
  akrun_sapply = {sapply(L1, function(x) which(x %in% v1))},
  akrun_Vectorize = {Vectorize(function(x) which(x %in% v1))(L1)},
  akrun_mapply = {mapply(function(x, y) which(x %in% y), L1, v1)},
  akrun_mapply_match = {mapply(match, v1, L1)},
  akrun_map2 = {purrr::map2_int(L1, v1, ~ .x %in% .y %>% which)},
  CPak = {setNames(rep(1:length(L1), times=lengths(L1)), unlist(L1))[as.character(v1)]},
  zacdav = {sequence(lengths(L1))[match(v1, unlist(L1))]},
  zacdav_which = {sequence(lengths(L1))[which(unlist(L1) %in% v1)]},
  times = 10000
)

Unit: microseconds
               expr     min       lq      mean   median       uq        max neval
       akrun_sapply  18.187  22.7555  27.17026  24.6140  27.8845   2428.194 10000
    akrun_Vectorize  60.119  76.1510  88.82623  83.4445  89.9680   2717.420 10000
       akrun_mapply  19.006  24.2100  29.78381  26.2120  29.9255   2911.252 10000
 akrun_mapply_match  14.136  18.4380  35.45528  20.0275  23.6560 127960.324 10000
         akrun_map2 217.209 264.7350 303.64609 277.5545 298.0455   9204.243 10000
               CPak  15.741  19.7525  27.31918  24.7150  29.0340    235.245 10000
             zacdav   6.649   9.3210  11.30229  10.4240  11.5540   2399.686 10000
       zacdav_which   7.364  10.2395  12.22632  11.2985  12.4515   2492.789 10000

list of vectors in R - extract an element of the vectors

lapply(data, function(x) substr(x[startsWith(x, "no")], 4, 1000))

[[1]]
[1] "more"

[[2]]
[1] "comfort" "one"    

Find Intersect of a Vector and List of Vectors

We could do

lapply(myList, intersect, y = myVector)
#$Fruits
#[1] "Banana" "Apple" 
#
#$Veggies
#[1] "Spinach" "Lettuce"
#
#$Other
#[1] "Soda"  "Candy"

Explanation: elements of myList are passed to x one by one; myVector is passed to y.

## check arguments of `intersect()`
args(intersect)
#function (x, y)

r - check is all elements of a list match a vector exactly

We can use lapply :

lapply(list_1, function(x) if(all(x %in% vec_1)) TRUE else setdiff(x, vec_1))

#$x
#[1] TRUE

#$y
#[1] "foo"  "bars"

Find all intersecting vectors in a list of vectors in R

Given that the list elements should be partitioned according to:

• List elements with empty intersections w.r.t. all the other list components,
• List elements with a non-empty intersection w.r.t. some other list component,

a way to achieve this in base R is as follows:

## find set components w/ empty intersections w/ all other components
isUnique <- sapply(seq_along(sets), function(i) length(intersect(sets[[i]], unlist(sets[-i]))) < 1)

## empty intersect components
sets[isUnique]
#> $e
#> [1] "e45" "e55" "e65"
#> 
#> $j
#> [1] "j1" "j2" "j3"

## non-empty intersect components 
sets[!isUnique]
#> $b
#> [1] "b4" "b5" "b6"
#> 
#> $c
#> [1] "c2" "c3" "b4" "b5" "c6"
#> 
#> $d
#> [1] "d1" "d2"
#> 
#> $f
#> [1] "f4" "f5" "d1" "f6"
#> 
#> $g
#> [1] "g1" "g2"
#> 
#> $h
#> [1] "h5" "h6" "h7"
#> 
#> $i
#> [1] "i9" "h5" "g1" "h6" "i8" "i7"

Find vector of strings in list (R)

%in% checks presence of elements of the LHS among elements of the RHS. To treat c("a", "b") as a single element of the RHS, it needs to be in a list:

which(l %in% list(c("a", "b")))

Other possibilities are to go element-by-element through l with sapply, such as

which(sapply(l,function(x) all(c("a","b") %in% x)))
# order doesn't matter, other elements allowed

which(sapply(l, identical, c("a", "b"))) # exact match, in order

R - How do I check if an element is in a list of vectors?

The most straightforward option is that you could store unique entries in another vector as you're looping through your input data.

Here's a solution without considering the positions (1 or 2) of the alphabets in your output list or the order of your input list.

dat <- list(c('a','d'),c('a','c'),c('d','e'),c('e','f'),c('b','c'),
            c('f','c'),c('c','e'),c('f','b'),c('b','a'))
Dat <- list()
idx <- list()
for(i in dat){
  if(!all(i %in% idx)){
    Dat <- append(Dat, list(i))
    ## append to idx if not previously observed
    if(! i[1] %in% idx) idx <- append(idx, i[1])
    if(! i[2] %in% idx) idx <- append(idx, i[2])
  }
}
print(Dat)
#> [[1]]
#> [1] "a" "d"
#> 
#> [[2]]
#> [1] "a" "c"
#> 
#> [[3]]
#> [1] "d" "e"
#> 
#> [[4]]
#> [1] "e" "f"
#> 
#> [[5]]
#> [1] "b" "c"

On another note, I'd advise against using T as your vector name as it's used as TRUE in R.

R: Find unique vectors in list of vectors

We can sort the list elements, apply duplicated to get a logical index of unique elements and subset the list based on that

list_of_vectors[!duplicated(lapply(list_of_vectors, sort))]
#[[1]]
#[1] "a" "b" "c"

#[[2]]
#[1] "b" "b" "c"

#[[3]]
#[1] "c" "c" "b"

#[[4]]
#[1] "b" "b" "c" "d"

#[[5]]
#NULL

---

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