[R] Select

[Val]

Thank you very much Jeff, Goran and David  for your help.


On Mon, Feb 11, 2019 at 6:22 PM Jeff Newmiller <jdnewmil using dcn.davis.ca.us> wrote:
>
> N <- 8 # however many times you want to do this
> ans <- lapply( seq.int( N )
>               , function( n ) {
>                   idx <- sample( nrow( mydat ) )
>                   mydat[ idx[ seq.int( which( 40 < cumsum( mydat[ idx, "count" ] ) )[ 1 ] ) ], ]
>                 }
>               )
>
>
> On Mon, 11 Feb 2019, Val wrote:
>
> > Sorry Jeff and David  for not being clear!
> >
> > The total sample size should be at least 40, but the selection should
> > be based on group ID.  A different combination of Group ID could give
> > at least  40.
> > If I select  group G1   with 25  count and  G2  and with 15  counts
> > then   I can get  a minimum of 40  counts.   So G1 and G2 are
> > selected.
> > G1  25
> > G2  15
> >
> > In another scenario, if G2, G3 and G4  are  selected  then the total
> > count will be 58 which is  greater than 40. So G2 , G3 and G4  could
> > be selected.
> > G2 15
> > G3 12
> > G4 31
> >
> > So the restriction is to  find group IDs  that give a minim of  40.
> > Once, I reached a minim of 40 then stop selecting group  and output
> > the data..
> >
> > I am hope this helps
> >
> >
> >
> >
> > On Mon, Feb 11, 2019 at 5:09 PM Jeff Newmiller <jdnewmil using dcn.davis.ca.us> wrote:
> >>
> >> This constraint was not clear in your original sample data set. Can you expand the data set to clarify how this requirement REALLY works?
> >>
> >> On February 11, 2019 3:00:15 PM PST, Val <valkremk using gmail.com> wrote:
> >>> Thank you David.
> >>>
> >>> However, this will not work for me. If the group ID selected then all
> >>> of its observation should be included.
> >>>
> >>> On Mon, Feb 11, 2019 at 4:51 PM David L Carlson <dcarlson using tamu.edu>
> >>> wrote:
> >>>>
> >>>> First expand your data frame into a vector where G1 is repeated 25
> >>> times, G2 is repeated 15 times, etc. Then draw random samples of 40
> >>> from that vector:
> >>>>
> >>>>> grp <- rep(mydat$group, mydat$count)
> >>>>> grp.sam <- sample(grp, 40)
> >>>>> table(grp.sam)
> >>>> grp.sam
> >>>> G1 G2 G3 G4 G5
> >>>> 10  9  5 13  3
> >>>>
> >>>> ----------------------------------------
> >>>> David L Carlson
> >>>> Department of Anthropology
> >>>> Texas A&M University
> >>>> College Station, TX 77843-4352
> >>>>
> >>>>
> >>>> -----Original Message-----
> >>>> From: R-help <r-help-bounces using r-project.org> On Behalf Of Val
> >>>> Sent: Monday, February 11, 2019 4:36 PM
> >>>> To: r-help using R-project.org (r-help using r-project.org)
> >>> <r-help using r-project.org>
> >>>> Subject: [R] Select
> >>>>
> >>>> Hi all,
> >>>>
> >>>> I have a data frame  with tow variables  group and its size.
> >>>> mydat<- read.table( text='group  count
> >>>> G1 25
> >>>> G2 15
> >>>> G3 12
> >>>> G4 31
> >>>> G5 10' , header = TRUE, as.is = TRUE )
> >>>>
> >>>> I want to select   group ID randomly (without replacement)  until
> >>> the
> >>>> sum of count reaches 40.
> >>>> So, in  the first case, the data frame could be
> >>>>    G4 31
> >>>>    65 10
> >>>>
> >>>> In other case, it could be
> >>>>   G5 10
> >>>>   G2 15
> >>>>   G3 12
> >>>>
> >>>> How do I put sum of count variable   is  a minimum of 40 restriction?
> >>>>
> >>>> Than k you in advance
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> I want to select group  ids randomly until I reach the
> >>>>
> >>>> ______________________________________________
> >>>> R-help using 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 using 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.
> >>
> >> --
> >> Sent from my phone. Please excuse my brevity.
> >
>
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