Difference between the == and %in% operators in R

%in% is value matching and “returns a vector of the positions of (first) matches of its first argument in its second” (See help('%in%')) This means you could compare vectors of different lengths to see if elements of one vector match at least one element in another. The length of output will be equal to the length of the vector being compared (the first one).

1:2 %in% rep(1:2,5)
#[1] TRUE TRUE

rep(1:2,5) %in% 1:2
#[1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE

#Note this output is longer in second

== is logical operator meant to compare if two things are exactly equal. If the vectors are of equal length, elements will be compared element-wise. If not, vectors will be recycled. The length of output will be equal to the length of the longer vector.

1:2 == rep(1:2,5)
#[1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE

rep(1:2,5) == 1:2
#[1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE

1:10 %in% 3:7
#[1] FALSE FALSE  TRUE  TRUE  TRUE  TRUE  TRUE FALSE FALSE FALSE

#is same as 

sapply(1:10, function(a) any(a == 3:7))
#[1] FALSE FALSE  TRUE  TRUE  TRUE  TRUE  TRUE FALSE FALSE FALSE

NOTE: If possible, try to use identical or all.equal instead of == and.

Related Posts:

  1. What exactly does += do in python?
  2. Use of “instanceof” in Java [duplicate]
  3. What are XAND and XOR
  4. What does the “+=” operator do in Java?
  5. ^=, -= and += symbols in Python
  6. assignment operator overloading in c++
  7. How to use operator ‘-replace’ in PowerShell to replace strings of texts with special characters and replace successfully
  8. What does the question mark character (‘?’) mean in C++?
  9. proper name for python * operator?
  10. What does the question mark character (‘?’) mean in C++?
  11. What is the ‘new’ keyword in JavaScript?
  12. What does the percentage sign mean in Python
  13. What is the idiomatic Go equivalent of C’s ternary operator?
  14. Not equal to != and !== in PHP
  15. What does the percentage sign mean in Python
  16. What does =~ do in Perl?
  17. Difference between “or” and || in Ruby?
  18. R: += (plus equals) and ++ (plus plus) equivalent from c++/c#/java, etc.?
  19. Difference between “and” and && in Ruby?

Leave a Comment