[R] How do I tell whether two vectors are identical?

[Łukasz Ręcławowicz]

> benchmark(
+  all_eq = {isTRUE(all.equal.numeric(x,y))},
+  dfrm = {compare<-data.frame(id<-seq(1,43e3,1),x,y);
+         compare$id[compare$x!=compare$y]},
+  int = {(compare$x!=compare$y)},
+  slf = {differences<-compare$id[compare$x!=compare$y]},
+  replications=1000)
    test replications elapsed  relative user.self sys.self
1 all_eq         1000   14.61 11.068182     12.59      0.02
2   dfrm         1000   27.08 20.515152      23.38     0.00
3      int         1000    1.32   1.000000       1.20      0.00
4      slf         1000    3.45   2.613636       2.91      0.00

Because:

a) in many real cases data frame may exist, so you create it only once
b) loop was "unfair" ;)
c) my approach gives an information about "the indices of positions at which
the vectors differ"
Time of "evaluation of differences" is also mesured, not only
assignment to vector.

Summary:
If you already got a data frame, slf method can be a few times faster.
If you don't have it, and you only need to know are they differ as a
whole check by all_eq. It depends on needs and stored format.

W dniu 13 października 2010 00:16 użytkownik David Winsemius
<dwinsemius at comcast.net> napisał:

> And as a result you have chosen not to include the creation of the
> data.frame inside your loop.
>
> David Winsemius, MD
> West Hartford, CT




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