Date:         Fri, 10 Feb 2006 11:05:44 -0800
Reply-To:     Dale Remus <hellangel_987@YAHOO.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Dale Remus <hellangel_987@YAHOO.COM>
Subject:      sampling based on weighted probability
In-Reply-To:  <BAY101-F23FB03FF59708E17888664DE030@phx.gbl>
Content-Type: text/plain; charset=iso-8859-1

Hi,

I'd like to present my question in a much simplified
way:

I have a data set with variable x and weight:

x   weight
1    0.3
2    0.2
3    0.4
4    0.07
5    0.03

(note that sum of the weight is 1)

I need to take a sample of size, say 2, from x, but
not random sampling: x is to be selected with
probability of the corresponding weight, for example,
with probability 0.3, x=1 is selected.

I am very frustrated that while this job can be done
in R as easily as one line statement
sample(x,2,prob=w),
SAS technicians couldn't even understand my question
after more than one follow-up.  Every time they
directed me to PROC SURVEYSELECT using options
 METHOD=PPS. I have read through the SAS manual
carefully, I am positive this is not the same issue.
It seems to me they've never heard of any sampling
scheme other than simple random sample.

As a graduate student at Statistics department, I had
been enjoying writing codes in R for 3 years mainly
because that almost all academic professionals prefer
R to SAS, believing the former a research-oriented
programming language while the latter merely a tool to
manipulate data. But I myself have turned back to SAS
as I found that R is easily broken down with moderate
to large size data while SAS has the amazing capacity
and efficiency of huge data prosessing which
insurmountable by R. I have ever since implemented all
of our algorithms in SAS. But the lack of flexibility,
the lack of easy-used functions of SAS have made my
life increasing difficult as our research project
getting more and more complicated.


Thank you for lisening to my blah blah.

Dale

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