If else building block

Question

Is there an equivalent building block in R for

if ($a > $b) {
    echo "a is bigger than b";
} elseif ($a == $b) {
    echo "a is equal to b";
} else {
    echo "a is smaller than b";
}

from PHP or Java?

Maybe [this][1] "switch" can help you? [1]: http://stackoverflow.com/questions/10393508/how-to-use-the-switch-statement-in-r-functions — LostAvatar, Sep 02 '13 at 08:10
For the people who know R but not PHP or Java perhaps describe what `echo` does. Maybe also add the result you want to your post. Maybe also add the PHP and Java tags to your post. — Mark Miller, Sep 02 '13 at 08:30

score 3 · Accepted Answer · edited Sep 02 '13 at 12:02

3

It's not idiomatic but the answer is yes:

if (a > b) {
  cat("a is bigger than b")
} else if (a == b) {
  cat("a is equal to b")
} else {
  cat("a is smaller than b")
}

edited Sep 02 '13 at 12:02

flodel

answered Sep 02 '13 at 08:32

user2739139

Maybe worth explaining that this is not idiomatic because it is not vectorised. The `ifelse` function is a vectorised alternative. Also, I'd be tempted by `message` rather than `cat` (which is low level and not really meant to be called directly). – Richie Cotton Sep 02 '13 at 12:03
Also worth explaining that the curly braces (my edit) are necessary to avoid the possibility that R reads the first two lines as a complete statement then throw `Error: unexpected ’else’ in "else"`. – flodel Sep 02 '13 at 12:08
@Richie ```message``` is probably to be recommended but I suppose ```cat``` is arguably closer to ```echo```. – user2739139 Sep 03 '13 at 00:42
@flodel That is a good correction. The other option is to put the ```else``` before the line break. Although all work (including the original) if it is defined within a function. – user2739139 Sep 03 '13 at 00:44

1 Answers1