Comparing two vectors in an if statement

Question

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 ?

Answer 1

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.

Answer 2

Are they identical?

> identical(A,C) [1] FALSE 

Which elements disagree:

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