The difference between & and && in R

Question

I have read

http://stat.ethz.ch/R-manual/R-devel/library/base/html/Logic.html

and the difference between & and && doesn\'t make sense. For examp

Answer 1

The "&" operator is only an element -by-element logical AND when the vectors are of equal length. That why you should also expect this result:

 c(0,1,2,3,4) & 1
[1] FALSE  TRUE  TRUE  TRUE  TRUE  # due to argument recycling

Notice that it is not comparing numerical values but only after coercion to type "logical", and any non-zero value will be TRUE:

seq(0,1,by=.2) & -1
[1] FALSE  TRUE  TRUE  TRUE  TRUE  TRUE

"&&" only compares the first element of its first argument to the first argument of the second and issues a warning (but not an error) if either are longer than a single element.

If you want to test for equality then use "==".