It all has to do with the precedence of the ! operator.
Compare !duplicated(v) + 0 with (!duplicated(v)) + 0
Dave
From:
"Charles C. Berry" <cbe...@tajo.ucsd.edu>
To:
Dennis Murphy <djmu...@gmail.com>
Cc:
r-help@r-project.org
Date:
11/23/2010 10:08 AM
Subject:
Re: [R] the first. from SAS in R
Sent by:
r-help-boun...@r-project.org
On Tue, 23 Nov 2010, Dennis Murphy wrote:
> Interesting. Check this out:
>
> u <- sample(c(TRUE, FALSE), 10, replace = TRUE)
>> u
> [1] FALSE FALSE TRUE FALSE FALSE TRUE FALSE FALSE FALSE FALSE
>> class(u)
> [1] "logical"
>> u + 0
> [1] 0 0 1 0 0 1 0 0 0 0
>> 0 + u
> [1] 0 0 1 0 0 1 0 0 0 0
>
> v <- rpois(10, 3)
>> !duplicated(v)
> [1] TRUE FALSE TRUE TRUE TRUE TRUE FALSE TRUE FALSE TRUE
>> class(!duplicated(v))
> [1] "logical"
>> !duplicated(v) + 0
> [1] TRUE FALSE TRUE TRUE TRUE TRUE FALSE TRUE FALSE TRUE
>> 0 + !duplicated(v)
> [1] 1 0 1 1 1 1 0 1 0 1
>
> # Now assign !duplicated(v) to an object:
>> w <- !duplicated(v)
>> class(w)
> [1] "logical"
>> 0 + w
> [1] 1 0 1 1 1 1 0 1 0 1
>> w + 0
> [1] 1 0 1 1 1 1 0 1 0 1
>
> I can see *what* is going on, but what is the reason for it? I see
another
> notebook entry coming :)
See
?Arithmetic
and read the paragraph under Details starting 'Logical vectors'
Chuck
>
> Dennis
>
> On Tue, Nov 23, 2010 at 6:12 AM, David Winsemius
<dwinsem...@comcast.net>wrote:
>
>>
>> On Nov 23, 2010, at 8:33 AM, Joel wrote:
>>
>>
>>> Is there any similar function in R to the first. in SAS?
>>>
>>> What it dose is:
>>>
>>> Lets say we have this table:
>>>
>>> a b c
>>> 1 1 5
>>> 1 0 2
>>> 2 0 2
>>> 2 0 NA
>>> 2 9 2
>>> 3 1 3
>>>
>>>
>>> and then I want do to do one thing the first time the number 1 appers
in a
>>> and something else the secund time 1 appers in a and so on.
>>>
>>> so
>>>
>>> something similar to:
>>>
>>> if first.a {
>>> a$d<-1
>>> }else{
>>> a$d<-0
>>> }
>>>
>>>
>> The duplicated function which returns a logical vector with those
features
>> can easily be coerced to numeric.
>>
>> df$d <- as.numeric(!duplicated(df$a))
>>
>>
>> I was a bit puzzled about my failure to get coercion by the method
which I
>> thought was supposed to work, namely adding 0.
>>
>> df$e <- !duplicated(df$a)+0 # does not coerce
>>
>> df$e <- 0 + !duplicated(df$a) # pre-adding 0 does coerce
>>
>> Maybe the rules on coercion were amended.
>>
>> --
>> David
>>
>>
>> This would give me
>>>
>>> a b c b
>>> 1 1 5 1
>>> 1 0 2 0
>>> 2 0 2 1
>>> 2 0 NA 0
>>> 2 9 2 0
>>> 3 1 3 1
>>>
>>> Is there such a function in R or anything similar?
>>>
>>>
>>> thx
>>>
>>> //Joel
>>>
>>> --
>>> View this message in context:
>>>
http://r.789695.n4.nabble.com/the-first-from-SAS-in-R-tp3055417p3055417.html
>>> Sent from the R help mailing list archive at Nabble.com.
>>>
>>> ______________________________________________
>>> R-help@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.
>>>
>>
>> David Winsemius, MD
>> West Hartford, CT
>>
>>
>> ______________________________________________
>> R-help@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.
>>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@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.
>
Charles C. Berry Dept of Family/Preventive
Medicine
cbe...@tajo.ucsd.edu UC
San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
______________________________________________
R-help@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.
[[alternative HTML version deleted]]
______________________________________________
R-help@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.
