let say vector x = c(33, 22, 45)
In the reference code the function body says, take index of x and inside the index don't keep the value matched with x. If say the value is 45 and it removed from x inside the indexing then in outer of indexing i.e. x [ ] how it restoring the 33 and 22. I'm little bit confused with this function, how actually it keeping the index 1 and 2 as 33 and 22.
why not it returning x[33,22] which provides NA values but actually it taking the values like x[1,2] excluding the 33 at 3rd index position.
May be I'm not getting it properly. Can anyone please elaborate how the code is producing 33 and 22 as output?
A code example is attached in .JPG format
***** This code is for R programming language.
This is R basics (and, in some cases, general programming basics); you can find the answers to these questions in any introduction to R. In fact, you will learn this better if you investigate it a bit yourself rather than just asking. However, if you do need the answers:
- %in% is an operator that returns TRUE if the thing on the left appears anywhere in the thing on the right (i.e., if sume number appears in a list of possible numbers).
- value is some list of list of numbers. So `x %in% value` returns TRUE if x is in the list, FALSE otherwise
- ! means 'not'. So it changes true into false, or false into true. Basic boolean operator.
- "erase
I'll add a couple of comments.
1) Using R, it's easy to look up the meaning of functions:
?"%in%"
?"!"
for most functions you don't need the quotes:
?mean
2) The function is a little unusual in its form. More typically, the function would be written as:
erase
I agree; I had never seen this kind of in-place replacement function in R before reading this question. I don't quite see why you would want to use it; I'm pretty sure R was designed with specific reasons not to do in-place changes to things.
I'm learning data science with R and in a book this examples were provided in function section. After reading this type of functions, I was wondering how it is actually working as it was little bit surprise for me. I have never seen this kind of function and even in stack overflow i haven't found this type of function.
Thanks everyone for your reply
The %in% function returns true and false values.
Try:
Sal = c(99, 100, 101, 102)
Sal %in% 99
Sal[c(TRUE, FALSE, TRUE, FALSE)]
Same as:
Sal[c(1,3)]
Sir, Thanks for your answer
I also got the answer from stack overflow; posted by Ryan
http://stackoverflow.com/a/42751819/7382467
The vector x %in% 45 checks whether each element of x is in 45 and records TRUE if it is, else FALSE (since 45 is a single value, this is the same as x == 45).
So x %in% 45 == c(FALSE, FALSE, TRUE)
Then the ! operator reverses logical values, so
! x %in% 45 == c(TRUE, TRUE, FALSE)
When we subset by entering a logical vector in [ ], the values of the vector whose indexes correspond to the value FALSE in the logical vector are removed. In this case, only 45 has an index (3) whose value in the logical vector is FALSE, so it is removed.
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