round() and negative digits

On 11-10-08 5:32 PM, Rolf Turner wrote:

On 09/10/11 00:18, Duncan Murdoch wrote:

On 11-10-07 5:26 PM, Carl Witthoft wrote:

Just wondering here -- I tested and found to my delight that

%  round(325.4,-2)
[1] 300

gave me exactly what I would have expected (and wanted).
Since it's not explicitly mentioned in the documentation
that negative 'digits' is allowed, I just wanted to ask
whether this behavior is intentional or a happy turn of
events. I'm always paranoid that something not explicitly
documented might disappear in future revisons.

It is intentional, and one of the regression tests confirms
that it's there, so it won't disappear by mistake, and would
be very unlikely to disappear intentionally.

Uh, wouldn't it be *nice* to mention this --- not completely
obvious --- capability in the help file?

If we told you all of R's secrets, we'd have to kill you.

Duncan Murdoch

A Fortunate remark??

That being said -- if such are your intentions, then over
my dead body ...

Carl Witthoft's serendipitous discovery is a nice example
of how secrets can be guessed by wondering "what if ... ?".
So probably you don;t need to tell the secrets.

Taking the "negative digits" to their logical extreme:

  round(654.321,2)
  # [1] 654.32
  round(654.321,1)
  # [1] 654.3
  round(654.321,0)
  # [1] 654
  round(654.321,-1)
  # [1] 650
  round(654.321,-2)
  # [1] 700
  round(654.321,-3)
  # [1] 1000
  round(654.321,-4)
  # [1] 0

which is what you'd logically expect (but is it what you
would intuitively expect?).

Ted.

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Date: 08-Oct-11                                       Time: 23:11:27
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