# Comparing two vectors in an if statement

41

I want put stop condition inside a function. The condition is that if first and second elements should match perfectly in order and length.

``````A <- c("A", "B", "C", "D")
B <- A
C <- c("A", "C", "C", "E")

> A == B
 TRUE TRUE TRUE TRUE
``````

This is good situation to go forward

``````> A == C

  TRUE  FALSE TRUE FALSE
``````

Since there is one false this condition to stop and output that the condition doesnot hold at 2 and 4 th column.

``````if (A != B) {
stop("error the A and B does not match at column 2 and 4"} else {
cat ("I am fine")
}
Warning message:
In if (A != B) (stop("error 1")) :
the condition has length > 1 and only the first element will be used
``````

Am I missing something obvious ? Also I can output where error positions are ?

This question is tagged with `r` `loops` `operators` `dataframe`

~ Asked on 2012-04-29 18:48:36

### The Best Answer is

64

`all` is one option:

``````> A <- c("A", "B", "C", "D")
> B <- A
> C <- c("A", "C", "C", "E")

> all(A==B)
 TRUE
> all(A==C)
 FALSE
``````

But you may have to watch out for recycling:

``````> D <- c("A","B","A","B")
> E <- c("A","B")
> all(D==E)
 TRUE
> all(length(D)==length(E)) && all(D==E)
 FALSE
``````

The documentation for `length` says it currently only outputs an integer of length 1, but that it may change in the future, so that's why I wrapped the length test in `all`.

~ Answered on 2012-04-29 20:34:34

29

Are they identical?

``````> identical(A,C)
 FALSE
``````

Which elements disagree:

``````> which(A != C)
 2 4
``````

~ Answered on 2012-04-29 18:53:14