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
[1] TRUE TRUE TRUE TRUE

This is good situation to go forward

> A == C

[1]  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)
[1] TRUE
> all(A==C)
[1] FALSE

But you may have to watch out for recycling:

> D <- c("A","B","A","B")
> E <- c("A","B")
> all(D==E)
[1] TRUE
> all(length(D)==length(E)) && all(D==E)
[1] 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)
[1] FALSE

Which elements disagree:

> which(A != C)
[1] 2 4

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


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