R help - Jul 2012 - Is it possible to remove this loop? [SEC=UNCLASSIFIED]

Hi all,

I would like create a new column in a data.frame (a1) to store 0, 1 data
converted from a factor as below.

a1$h2<-NULL
for (i in 1:dim(a1)[1]) {
      if (a1$h1[i]=="H") a1$h2[i]<-1 else a1$h2[i]<-0
      }

My question: is it possible to remove the loop from above code to achieve the
desired result?

Thanks in advance,
Jin

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Hello,

Try:

 > a1$h2 <- 0
 > a1$h2[a1$h1=="H"] <- 1

Regards

Le 12/07/03 16:18, Jin.Li at ga.gov.au a ?crit :
> Hi all,
>
> I would like create a new column in a data.frame (a1) to store 0, 1 data
converted from a factor as below.
>
> a1$h2<-NULL
> for (i in 1:dim(a1)[1]) {
>        if (a1$h1[i]=="H") a1$h2[i]<-1 else a1$h2[i]<-0
>        }
>
> My question: is it possible to remove the loop from above code to achieve
the desired result?
>
> Thanks in advance,
> Jin
>
> Geoscience Australia Disclaimer: This e-mail (and files transmitted with
it) is intended only for the person or entity to which it is addressed. If you
are not the intended recipient, then you have received this e-mail by mistake
and any use, dissemination, forwarding, printing or copying of this e-mail and
its file attachments is prohibited. The security of emails transmitted cannot be
guaranteed; by forwarding or replying to this email, you acknowledge and accept
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>
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>
>
> 	[[alternative HTML version deleted]]
>
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>

Hi
> Hi all,
> 
> I would like create a new column in a data.frame (a1) to store 0, 1 data 
> converted from a factor as below.
> 
> a1$h2<-NULL
> for (i in 1:dim(a1)[1]) {
>       if (a1$h1[i]=="H") a1$h2[i]<-1 else a1$h2[i]<-0
>       }
> 
> My question: is it possible to remove the loop from above code to 
achieve 
> the desired result?
Untested

a1$h2 <- (a1$h1=="H")*1

Regards
Petr
> 
> Thanks in advance,
> Jin
> 
> Geoscience Australia Disclaimer: This e-mail (and files transmitted with 
> it) is intended only for the person or entity to which it is addressed. 
If
> you are not the intended recipient, then you have received this e-mail 
by 
> mistake and any use, dissemination, forwarding, printing or copying of 
> this e-mail and its file attachments is prohibited. The security of 
emails
> transmitted cannot be guaranteed; by forwarding or replying to this 
email,
> you acknowledge and accept these risks.
> 
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> 
> 
>    [[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

On 07/03/2012 05:18 PM, Jin.Li at ga.gov.au wrote:
> Hi all,
>
> I would like create a new column in a data.frame (a1) to store 0, 1 data
converted from a factor as below.
>
> a1$h2<-NULL
> for (i in 1:dim(a1)[1]) {
>        if (a1$h1[i]=="H") a1$h2[i]<-1 else a1$h2[i]<-0
>        }
>
> My question: is it possible to remove the loop from above code to achieve
the desired result?
>
Hi Jin,
Just to provide you with an embarrassment of alternatives:

a1$h2<-ifelse(a1$h1=="H",1,0)

Jim

And one more alternative:

a1$h2 <- apply(a1,1, function(x)  if (x["h1"]=="H") 1
else 0 )

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Thank you all for providing various alternatives. They are all pretty fast.
Great help! Based on a test of a dataset with 800,000 rows, the time used varies
from 0.04 to 11.56 s. The champion is:
> a1$h2 <- 0
> a1$h2[a1$h1=="H"] <- 1
Regards,
Jin

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intended only for the person or entity to which it is addressed. If you are not
the intended recipient, then you have received this e-mail by mistake and any
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