[R] rounding up (always)

[David Winsemius]

On Oct 20, 2010, at 8:38 PM, Dimitri Liakhovitski wrote:

> Thank you for your help, everyone.
> Actually, I am building a lot of graphs (in a loop) but the values on
> the y axes from graph to graph could range from [-5; 5] to [-10,000;
> 10,000].
> So, I am trying to create ylim ranging from ymin to ymax such that
> they look appropriate for the range.
> For example, if we are taking the actual range from -4.28 to 6.45, I'd
> like the range to be -5 to 7.
> But if the range is from -1225 to 2248, then I'd like it to be from
> -1500 to 2500 or from -2000 to 3000.
> Hence, my original question.

Except you did not express that desire correctly. And you still have  
not been very clear about the degree of rounding-ness needed. The  
first example above suggests to the next highest absolute value if the  
minimum is less than 10. (I didn't acheive that.)  You initially  
wanted the rounding to the next regular interval on the usual meaning  
of "greater than" when you wrote ... "always up"  ... and ... "higher"  
which would not lead most people to deliver an answer that satisfies  
your more recent specification.

In particular any log()-ging would need to first apply an abs()  
function. See if this is any more applicable to the (new) problem  
statement. This rounds out on both the negative and positive sides to  
the next highest power of 10.

 > roundout3 <- function(x){k=floor(log(abs(x),10)+1);
           sign(x)*ifelse(x==0, 0,  (floor( abs(x/10^k) 
+0.499999999999 ) +1)*10^k)}
# zero is a problem since log(0) and log(abs(0)) both return Inf.

 > roundout3(c(-1250,-250, -3, 0, 4, 250, 1250))
[1] -10000  -1000    -10      0     10   1000  10000

-- 
David.




> Dimitri
>
> On Wed, Oct 20, 2010 at 5:55 PM, Ted Harding  
> <ted.harding at wlandres.net> wrote:
>> On 20-Oct-10 21:27:46, Duncan Murdoch wrote:
>>> On 20/10/2010 5:16 PM, Dimitri Liakhovitski wrote:
>>>> Hello!
>>>>
>>>> I am trying to round the number always up - i.e., whatever the
>>>> positive number is, I would like it to round it to the closest 10  
>>>> that
>>>> is higher than this number, the closest 100 that is higher than  
>>>> this
>>>> number, etc.
>>>>
>>>> For example:
>>>> x<-3241.388
>>>>
>>>> signif(x,1) rounds to the closest thousand, i.e., to 3,000, but I'd
>>>> like to get 4,000 instead.
>>>> signif(x,2) rounds to the closest hundred, i.e., to 3,200, but I'd
>>>> like to get 3,300 instead.
>>>> signif(x,3) rounds to the closest ten, i.e., to 3,240, but I'd  
>>>> like to
>>>> get 3,250 instead.
>>>>
>>>> Of course, I could do:
>>>> floor(signif(x,1)+1000)
>>>> floor(signif(x,2)+100)
>>>> floor(signif(x,3)+10)
>>>>
>>>> But it's very manual - because in the problem I am facing the  
>>>> numbers
>>>> sometimes have to be rounded to a 1000, sometimes to a 100, etc.
>>>
>>> Write a function.  You have very particular needs, so it's unlikely
>>> there's already one out there that matches them.
>>> Duncan Murdoch
>>
>> As Duncan and Clint suggest, writing a function is straightforward:
>> for the problem as you have stated it, on the lines of
>>
>>  function(x,k){floor(signif(x,k-as.integer(log(x,10)-1))) + 10^k}
>>
>> However, what do you *really* want to happen to 3000?
>>
>> Ted.
>>
>> --------------------------------------------------------------------
>> E-Mail: (Ted Harding) <ted.harding at wlandres.net>
>> Fax-to-email: +44 (0)870 094 0861
>> Date: 20-Oct-10                                       Time: 22:55:47
>> ------------------------------ XFMail ------------------------------
>>
>
>
>
> -- 
> Dimitri Liakhovitski
> Ninah Consulting
> www.ninah.com
>
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David Winsemius, MD
West Hartford, CT