[R] Getting all possible combinations

Bert Gunter bgunter.4567 at gmail.com
Wed Aug 23 23:12:35 CEST 2017


Inline.

-- Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Wed, Aug 23, 2017 at 1:58 PM, peter dalgaard <pdalgd at gmail.com> wrote:
>
>> On 23 Aug 2017, at 20:51 , Ista Zahn <istazahn at gmail.com> wrote:
>>
>> On Wed, Aug 23, 2017 at 12:35 PM, Bert Gunter <bgunter.4567 at gmail.com> wrote:
>>> ummm, Ista, it's 2^n.
>>
>> ummm yes ughhhh.
>>
>
> You didn't really say otherwise: sum(choose(n,0:n)) == 2^n by the binomial expansion of (1+1)^n (but you knew that)
>
> This points to a different algorithm where you write 0:(2^n-1) as n-digit binary numbers and chose items corresponding to the 1s. That won't give the combinations **sorted by size of selected subgroup** though. Something like this:

No it doesn't.
-- Bert

>
> M <- as.matrix(do.call(expand.grid, rep(list(0:1),5)))
> mode(M) <- "logical"
> apply(M,1,function(i)LETTERS[1:5][i])
>
> -pd
>
>
>> My point is, if the number of groups is large, check it before hand.
>> If you can check it without embarrassing yourself in public like I did
>> that's even better.
>>
>> Best,
>> Ista
>>
>>>
>>> Cheers,
>>> Bert
>>>
>>>
>>> Bert Gunter
>>>
>>> "The trouble with having an open mind is that people keep coming along
>>> and sticking things into it."
>>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>>
>>>
>>> On Wed, Aug 23, 2017 at 8:52 AM, Ista Zahn <istazahn at gmail.com> wrote:
>>>> On Wed, Aug 23, 2017 at 11:33 AM, Christofer Bogaso
>>>> <bogaso.christofer at gmail.com> wrote:
>>>>> Hi again,
>>>>>
>>>>> I am exploring if R can help me to get all possible combinations of
>>>>> members in a group.
>>>>>
>>>>> Let say I have a group with 5 members : A, B, C, D, E
>>>>>
>>>>> Now I want to generate all possible unique combinations with all
>>>>> possible lengths from that group e.g.
>>>>>
>>>>> 1st combination : A
>>>>> 2nd combination : B
>>>>> .....
>>>>> 5th combination : E
>>>>> 6th combination : A, B
>>>>> 7th combination : B, C
>>>>> ....
>>>>> last combination: A, B, C, D, E
>>>>>
>>>>> Ideally, I have a fairly large group so am looking for some
>>>>> programmatic way to generate all possible combinations.
>>>>
>>>> Be careful, the number of combinations grows pretty quickly. You can
>>>> calculate the number ahead of time with
>>>>
>>>> sum(choose(n, 1:n))
>>>>
>>>> where n is the number of values in your group.
>>>>
>>>> --Ista
>>>>
>>>>>
>>>>> Any help will be highly appreciated.
>>>>>
>>>>> Thanks for your time.
>>>>>
>>>>> ______________________________________________
>>>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>>> 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 at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>> 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 at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> 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.
>
> --
> Peter Dalgaard, Professor,
> Center for Statistics, Copenhagen Business School
> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
> Phone: (+45)38153501
> Office: A 4.23
> Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com
>
>
>
>
>
>
>
>
>



More information about the R-help mailing list