# [R] Select

Val v@|kremk @end|ng |rom gm@||@com
Tue Feb 12 00:31:27 CET 2019

```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
> >>
> >> ______________________________________________
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> >> and provide commented, minimal, self-contained, reproducible code.
> >
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