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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[Pascal Oettli-2]

Hello,

Try:

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

Regards

Le 12/07/03 16:18, [hidden email] a écrit :

> 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 these risks.
> -------------------------------------------------------------------------------------------------------------------------
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] 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.
>

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[PIKAL Petr]

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.
>
-------------------------------------------------------------------------------------------------------------------------
>
>
>    [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] 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.

______________________________________________
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[Jim Lemon]

On 07/03/2012 05:18 PM, [hidden email] 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

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[Bart Joosen]

And one more alternative:

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

[David Winsemius]

On Jul 3, 2012, at 5:08 AM, Jim Lemon wrote:

> On 07/03/2012 05:18 PM, [hidden email] 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)

One more. Similar to Petr's, but perhaps a bit more accessible to a  
new R user:

a1$h2 <- as.numeric(a1$h1=="H")

I wasn't sure whether NA's would be handled in the same manner by  
these two methods so I tested:

 > ifelse( factor(c("H", "h", NA))=="H", 1, 0)
[1]  1  0 NA
 > as.numeric( factor(c("H", "h", NA))=="H")
[1]  1  0 NA

--
David Winsemius, MD
West Hartford, CT

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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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[Peter Ehlers]

On 2012-07-03 17:23, [hidden email] wrote:
> 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

Interesting. My testing shows that Petr's solution is about
twice as fast. Not that it matters much - the time is pretty
small in any case.

  a0 <- data.frame(h1 = sample(c("H","J","K"), 1e7, replace = TRUE),
                   stringsAsFactors = FALSE)
  a1 <- a0
  system.time({a1$h2 <- 0; a1$h2[a1$h1 == "H"] <- 1})
  #   user  system elapsed
  #   1.47    0.48    1.96
  a11 <- a1

  a1 <- a0
  system.time(a1$h2 <- (a1$h1 == "H") * 1)
  #  user  system elapsed
  #  0.37    0.17    0.56
  a12 <- a1
  all.equal(a11,a12)
  #[1] TRUE

Peter Ehlers

> Regards,
> 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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[Pascal Oettli-2]

Le 04/07/2012 12:43, Peter Ehlers a écrit :

> On 2012-07-03 17:23, [hidden email] wrote:
>> 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$h1=="H"] <- 1
>
> Interesting. My testing shows that Petr's solution is about
> twice as fast. Not that it matters much - the time is pretty
> small in any case.
>
>   a0 <- data.frame(h1 = sample(c("H","J","K"), 1e7, replace = TRUE),
>                    stringsAsFactors = FALSE)
>   a1 <- a0
>   system.time({a1$h2 <- 0; a1$h2[a1$h1 == "H"] <- 1})
>   #   user  system elapsed
>   #   1.47    0.48    1.96
>   a11 <- a1
>
>   a1 <- a0
>   system.time(a1$h2 <- (a1$h1 == "H") * 1)
>   #  user  system elapsed
>   #  0.37    0.17    0.56
>   a12 <- a1
>   all.equal(a11,a12)
>   #[1] TRUE
>
> Peter Ehlers
>

I got the same result. Petr's solution is the fastest. Good to know it.

Pascal Oettli

>> Regards,
>> 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.
>
> ______________________________________________
> [hidden email] mailing list
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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Thanks for your validation. Yes Peter's solution is the fastest, faster than the previous one by saving 25% time. It was missed out in my previous testing.
Jin

-----Original Message-----
From: Pascal Oettli [mailto:[hidden email]]
Sent: Wednesday, 4 July 2012 2:07 PM
To: Li Jin
Cc: [hidden email]
Subject: Re: [R] Is it possible to remove this loop? [SEC=UNCLASSIFIED]



Le 04/07/2012 12:43, Peter Ehlers a écrit :

> On 2012-07-03 17:23, [hidden email] wrote:
>> 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$h1=="H"] <- 1
>
> Interesting. My testing shows that Petr's solution is about
> twice as fast. Not that it matters much - the time is pretty
> small in any case.
>
>   a0 <- data.frame(h1 = sample(c("H","J","K"), 1e7, replace = TRUE),
>                    stringsAsFactors = FALSE)
>   a1 <- a0
>   system.time({a1$h2 <- 0; a1$h2[a1$h1 == "H"] <- 1})
>   #   user  system elapsed
>   #   1.47    0.48    1.96
>   a11 <- a1
>
>   a1 <- a0
>   system.time(a1$h2 <- (a1$h1 == "H") * 1)
>   #  user  system elapsed
>   #  0.37    0.17    0.56
>   a12 <- a1
>   all.equal(a11,a12)
>   #[1] TRUE
>
> Peter Ehlers
>

I got the same result. Petr's solution is the fastest. Good to know it.

Pascal Oettli

>> Regards,
>> 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.
>
> ______________________________________________
> [hidden email] 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.
>

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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