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Merge branch 'master' of github.com:hadley/r4ds

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hadley 2016-03-10 08:46:12 -06:00
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functions.Rmd
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@ -146,7 +146,7 @@ Compared to the original, this code is easier to understand and we've eliminated
``` ```
1. Read the [complete lyrics](https://en.wikipedia.org/wiki/Little_Bunny_Foo_Foo) 1. Read the [complete lyrics](https://en.wikipedia.org/wiki/Little_Bunny_Foo_Foo)
to "Little Bunny Foo". There's a lot of duplication in this song. to "Little Bunny Foo Foo". There's a lot of duplication in this song.
Extend the initial piping example to recreate the complete song, and use Extend the initial piping example to recreate the complete song, and use
functions to reduce the duplication. functions to reduce the duplication.
@ -279,6 +279,14 @@ if (NA) {}
You can use `||` (or) and `&&` (and) to combine multiple logical expressions. These operators are "short-circuiting": as soon as `||` sees the first `TRUE` it returns `TRUE` without computing anything else. As soon as `&&` sees the first `FALSE` it returns `FALSE`. You should never use `|` or `&` in an `if` statement: these are vectorised operations that apply to multiple values. If you do have a logical vector, you can use `any()` or `all()` to collapse it to a single value. You can use `||` (or) and `&&` (and) to combine multiple logical expressions. These operators are "short-circuiting": as soon as `||` sees the first `TRUE` it returns `TRUE` without computing anything else. As soon as `&&` sees the first `FALSE` it returns `FALSE`. You should never use `|` or `&` in an `if` statement: these are vectorised operations that apply to multiple values. If you do have a logical vector, you can use `any()` or `all()` to collapse it to a single value.
You can enforce this more-strictly by using the `identical()` function, which returns either a single `TRUE` or a single `FALSE`. One thing to watch out for is that *you* have to be more strict when specifying integers:
```{r}
if (i == 0){}
if (identical(i, 0L)){}
```
### Multiple conditions ### Multiple conditions
You can chain multiple if statements together: You can chain multiple if statements together: