R help - Nov 2010 - truncate integers

Is there any really easy way to truncate integers with several consecutive
digits without rounding and without converting from numeric to character
(using strsplit, etc.)??  Something along these lines:

e.g. = 456

truncfun(e.g., location=1)
= 4

truncfun(e.g., location=1:2)
= 45

truncfun(e.g., location=2:3)
= 56

truncfun(e.g., location=3)
= 6

It's one thing using floor(x/100) to get 4 or floor(x/10) to get 45, but
I'd
like to return only 5 or only 6, for example, in cases where I don't know
what the numbers are going to be.

I'm sure there is something very logical that I am missing, but my code is
getting too complicated and I can't seem to find a parsimonious solution.

Tyler
-- 
View this message in context:
http://r.789695.n4.nabble.com/truncate-integers-tp3041086p3041086.html
Sent from the R help mailing list archive at Nabble.com.

On Nov 13, 2010, at 12:34 PM, T.D. Rudolph wrote:
>
> Is there any really easy way to truncate integers with several  
> consecutive
> digits without rounding and without converting from numeric to  
> character
> (using strsplit, etc.)??  Something along these lines:
>
> e.g. = 456
>
> truncfun(e.g., location=1)
> = 4
>
> truncfun(e.g., location=1:2)
> = 45
>
> truncfun(e.g., location=2:3)
> = 56
>
> truncfun(e.g., location=3)
> = 6
>
> It's one thing using floor(x/100) to get 4 or floor(x/10) to get 45,  
> but I'd
> like to return only 5 or only 6, for example, in cases where I don't  
> know
> what the numbers are going to be.
>
> I'm sure there is something very logical that I am missing, but my  
> code is
> getting too complicated and I can't seem to find a parsimonious  
> solution.
Modulo arithmetic? (not the same location arguments as you specified  
but should give you ideas to work with:

  trncint <- function(x, left=0,length=0)  (x %% 10^(left) ) %/%  
10^(left-length)

 > trncint(456, 2,2)
[1] 56
 > trncint(456, 3,2)
[1] 45
 > trncint(456, 3,1)
[1] 4
 > trncint(456, 2,1)
[1] 5
 > trncint(456, 3,1)
[1] 4

 > trncint(456, 1,1)
[1] 6

-- 

David Winsemius, MD
West Hartford, CT