Re: [R] Question about setdiff()

[Σταῦρος Μακράκης]

There are two kinds of set difference: the usual set difference
, also
called the asymmetric difference or relative complement, and the symmetric
difference .

In R, setdiff(a,b) is the usual asymmetric set difference, that is, all the
elements of a which are not elements of b. It is the set equivalent of the
logical expression (a and not b).

The symmetric difference consists of all the elements which appear in
either a or b, but not both. It is the set equivalent of logical xor.

I don't believe there is a standard R function for the symmetric
difference, but you can calculate it as

 symdiff <- function (a,b) setdiff(union(a,b),intersect(a,b))
or
 symdiff <- function(a,b) unique( c( a[is.na(match(a,b))],
b[is.na(match(b,a))]
) )

Challenge: is there a shorter or more efficient way to calculate symdiff
using R primitives?

   -s


On Mon, Jun 2, 2014 at 2:57 AM, Raphael Päbst 
wrote:

> Hello everyone, I have a question which is probably rooted in my lack
> of understanding when it comes to math.
>
> I just did the following:
>
> v <- c(1:20)
> w <- c(11:30)
> setdiff(v, w)
>
> and got:
> 1 2 3 4 5 6 7 8 9 10
>
> Then I did the following:
> setdiff(w, v)
> and got, not surprisingly:
> 21 22 23 24 25 26 27 28 29 30
>
> Now I was originally expecting to get bot with the first call of
> setdiff(v, w) and couldn't find any reason not to expect this from
> ?setdiff()
>
> Am I missing somethin vital here or does setdiff() always give me the
> elements of the first set that are not in the second one and not those
> which are exclusive to either one, just dropping the ones in the
> intersection of both sets?
>
> Many Thanks in advance
>
> Raphael
>
> __
> 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]]

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Re: [R] Question about setdiff()

[arun]

Hi,
Please check this link:
http://r.789695.n4.nabble.com/meaning-of-asymmetric-on-help-page-for-intersect-td877408.html

union(setdiff(v,w), setdiff(w,v))


#or in this case

setdiff(union(v,w),intersect(v,w))
#or
 setdiff(c(v,w),c(v,w)[duplicated(c(v,w))])
A.K.


.pae...@gmail.com> wrote:

Hello everyone, I have a question which is probably rooted in my lack
of understanding when it comes to math.

I just did the following:

v <- c(1:20)
w <- c(11:30)
setdiff(v, w)

and got:
1 2 3 4 5 6 7 8 9 10

Then I did the following:
setdiff(w, v)
and got, not surprisingly:
21 22 23 24 25 26 27 28 29 30

Now I was originally expecting to get bot with the first call of
setdiff(v, w) and couldn't find any reason not to expect this from
?setdiff()

Am I missing somethin vital here or does setdiff() always give me the
elements of the first set that are not in the second one and not those
which are exclusive to either one, just dropping the ones in the
intersection of both sets?

Many Thanks in advance

Raphael

__
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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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and provide commented, minimal, self-contained, reproducible code.

Re: [R] Question about setdiff()

[Raphael Päbst]

Thanks everyone!
It is just as I expected, I just didn't understand how setdiff() works.

Raphael

On 6/2/14, Pascal Oettli  wrote:
> Hello,
>
> From the help page: "Performs *set* union, intersection, (asymmetric!)
> difference, equality and membership on two vectors."
>
> Hope this helps,
> Pascal
>
>
> On Mon, Jun 2, 2014 at 3:57 PM, Raphael Päbst 
> wrote:
>> Hello everyone, I have a question which is probably rooted in my lack
>> of understanding when it comes to math.
>>
>> I just did the following:
>>
>> v <- c(1:20)
>> w <- c(11:30)
>> setdiff(v, w)
>>
>> and got:
>> 1 2 3 4 5 6 7 8 9 10
>>
>> Then I did the following:
>> setdiff(w, v)
>> and got, not surprisingly:
>> 21 22 23 24 25 26 27 28 29 30
>>
>> Now I was originally expecting to get bot with the first call of
>> setdiff(v, w) and couldn't find any reason not to expect this from
>> ?setdiff()
>>
>> Am I missing somethin vital here or does setdiff() always give me the
>> elements of the first set that are not in the second one and not those
>> which are exclusive to either one, just dropping the ones in the
>> intersection of both sets?
>>
>> Many Thanks in advance
>>
>> Raphael
>>
>> __
>> 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.
>
>
>
> --
> Pascal Oettli
> Project Scientist
> JAMSTEC
> Yokohama, Japan
>

__
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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.

Re: [R] Question about setdiff()

[Pascal Oettli]

Hello,

>From the help page: "Performs *set* union, intersection, (asymmetric!)
difference, equality and membership on two vectors."

Hope this helps,
Pascal


On Mon, Jun 2, 2014 at 3:57 PM, Raphael Päbst  wrote:
> Hello everyone, I have a question which is probably rooted in my lack
> of understanding when it comes to math.
>
> I just did the following:
>
> v <- c(1:20)
> w <- c(11:30)
> setdiff(v, w)
>
> and got:
> 1 2 3 4 5 6 7 8 9 10
>
> Then I did the following:
> setdiff(w, v)
> and got, not surprisingly:
> 21 22 23 24 25 26 27 28 29 30
>
> Now I was originally expecting to get bot with the first call of
> setdiff(v, w) and couldn't find any reason not to expect this from
> ?setdiff()
>
> Am I missing somethin vital here or does setdiff() always give me the
> elements of the first set that are not in the second one and not those
> which are exclusive to either one, just dropping the ones in the
> intersection of both sets?
>
> Many Thanks in advance
>
> Raphael
>
> __
> 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.



-- 
Pascal Oettli
Project Scientist
JAMSTEC
Yokohama, Japan

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Re: [R] Question about setdiff()

[Jeff Newmiller]

About time for you to adjust your expectations... looks right to me from both a 
mathematical sense and as the functions are designed.
---
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Sent from my phone. Please excuse my brevity.

On June 1, 2014 11:57:42 PM PDT, "Raphael Päbst"  
wrote:
>Hello everyone, I have a question which is probably rooted in my lack
>of understanding when it comes to math.
>
>I just did the following:
>
>v <- c(1:20)
>w <- c(11:30)
>setdiff(v, w)
>
>and got:
>1 2 3 4 5 6 7 8 9 10
>
>Then I did the following:
>setdiff(w, v)
>and got, not surprisingly:
>21 22 23 24 25 26 27 28 29 30
>
>Now I was originally expecting to get bot with the first call of
>setdiff(v, w) and couldn't find any reason not to expect this from
>?setdiff()
>
>Am I missing somethin vital here or does setdiff() always give me the
>elements of the first set that are not in the second one and not those
>which are exclusive to either one, just dropping the ones in the
>intersection of both sets?
>
>Many Thanks in advance
>
>Raphael
>
>__
>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.

__
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.