Re: [R] Coercion of percentages by as.numeric

From: Brandt, T. (Tobias) <TobiasBr_at_Taquanta.com>
Date: Tue 15 Nov 2005 - 04:07:42 EST

 

>-----Original Message-----
>From: Gabor Grothendieck [mailto:ggrothendieck@gmail.com]
>Sent: 14 November 2005 06:21 PM
>
>On 11/14/05, Brandt, T. (Tobias) <TobiasBr@taquanta.com> wrote:
>> Hi
>>
>> Given that things like the following work
>>
>> > a <- c("-.1"," 2.7 ","B")
>> > a
>> [1] "-.1" " 2.7 " "B"
>> > as.numeric(a)
>> [1] -0.1 2.7 NA
>> Warning message:
>> NAs introduced by coercion
>> >
>>
>> I naively expected that the following would behave differently.
>>
>> > b <- c('10%', '-20%', '30.0%', '.40%')
>> > b
>> [1] "10%" "-20%" "30.0%" ".40%"
>> > as.numeric(b)
>> [1] NA NA NA NA
>> Warning message:
>> NAs introduced by coercion
>
>Try this:
>
>as.numeric(sub("%", "e-2", b))
>

Thank you, that accomplishes what I had intended.

I would have thought though that the expression "53%" would be a fairly standard representation of the number 0.53 and might be handled as such. Is there a specific reason for avoiding this behaviour?

I can imagine that it might add unnecessary overhead to routines like "as.numeric" which one would like to keep as fast as possible.

Perhaps there are other areas though where it might be desirable? For example I'm thinking of the read.table function for reading in csv files since I have many of these that have been saved from excel and now contain numbers in the "%" format.



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