Test if a vector contains a given element

Question

How to check if a vector contains a given value

User · Answer

I will group the options based on output. Assume the following vector for all the examples.

v <- c('z', 'a','b','a','e')

For checking presence:

%in%

> 'a' %in% v
[1] TRUE

any()

> any('a'==v)
[1] TRUE

is.element()

> is.element('a', v)
[1] TRUE

For finding first occurance:

match()

> match('a', v)
[1] 2

For finding all occurances as vector of indices:

which()

> which('a' == v)
[1] 2 4

For finding all occurances as logical vector:

==

> 'a' == v
[1] FALSE  TRUE FALSE  TRUE FALSE

Edit: Removing grep() and grepl() from the list for reason mentioned in comments

User · Answer

You can use the  in  operator   vec  lt - c 1  2  3  4  5  1  in  vec   true 10  in  vec   false

User · Answer

Also to find the position of the element  which  can be used as  pop  lt - c 3 4 5 7 13   which pop  13    and to find the elements which are not contained in the target vector  one may do this   pop  lt - c 1 2 4 6 10   Tset  lt - c 2 10 7      Target set  pop which   pop in Tset

User · Answer

I really like grep   and grepl   for this purpose   grep   returns a vector of integers  which indicate where matches are   yo  lt - c  a    a    b    b    c    c    grep  b   yo   1  3 4   grepl   returns a logical vector  with  TRUE  at the location of matches   yo  lt - c  a    a    b    b    c    c    grepl  b   yo   1  FALSE FALSE  TRUE  TRUE FALSE FALSE   These functions are case-sensitive

User · Answer

The any   function makes for readable code   gt  w  lt - c 1 2 3   gt  any w  1   1  TRUE   gt  v  lt - c  a   b   c    gt  any v   b    1  TRUE   gt  any v   f    1  FALSE

User · Answer

Both the match    returns the first appearance  and  in   returns a Boolean  functions are designed for this   v  lt - c  a   b   c   e     b   in  v    returns TRUE  match  b  v     returns the first location of  b   in this case  2

User · Answer

is element   makes for more readable code  and is identical to  in   v  lt - c  a   b   c   e    is element  b   v   b   in  v    both return TRUE  is element  f   v   f   in  v    both return FALSE  subv  lt - c  a    f   subv  in  v    returns a vector TRUE FALSE is element subv  v     returns a vector TRUE FALSE

[r] Test if a vector contains a given element

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