[R] Counting non-empty levels of a factor

[John Kane]

With xx as your sample data will this work?  See ?addmargins

jj <- table(xx)

addmargins(jj, 2)

# or for both margins

addmargins(jj, c(1,2))

or 
apply(jj, 1, sum)


--- On Sun, 11/8/09, sylvain willart <sylvain.willart at gmail.com> wrote:

> From: sylvain willart <sylvain.willart at gmail.com>
> Subject: [R] Counting non-empty levels of a factor
> To: r-help at r-project.org
> Received: Sunday, November 8, 2009, 8:38 AM
> Hi everyone,
> 
> I'm struggling with a little problem for a while, and I'm
> wondering if
> anyone could help...
> 
> I have a dataset (from retailing industry) that indicates
> which brands
> are present in a panel of 500 stores,
> 
> store , brand
> 1 , B1
> 1 , B2
> 1 , B3
> 2 , B1
> 2 , B3
> 3 , B2
> 3 , B3
> 3 , B4
> 
> I would like to know how many brands are present in each
> store,
> 
> I tried:
> result <- aggregate(MyData$brand , by=list(MyData$store)
> , nlevels)
> 
> but I got:
> Group.1 x
> 1 , 4
> 2 , 4
> 3 , 4
> 
> which is not exactly the result I expected
> I would like to get sthg like:
> Group.1 x
> 1 , 3
> 2 , 2
> 3 , 3
> 
> Looking around, I found I can delete empty levels of factor
> using:
> problem.factor <- problem.factor[,drop=TRUE]
> But this solution isn't handy for me as I have many stores
> and should
> make a subset of my data for each store before dropping
> empty factor
> 
> I can't either counting the line for each store (N),
> because the same
> brand can appear several times in each store (several
> products for the
> same brand, and/or several weeks of observation)
> 
> I used to do this calculation using SAS with:
> proc freq data = MyData noprint ; by store ;
>  tables  brand / out = result ;
> run ;
> (the cool thing was I got a database I can merge with
> MyData)
> 
> any idea for doing that in R ?
> 
> Thanks in advance,
> 
> King Regards,
> 
> Sylvain Willart,
> PhD Marketing,
> IAE Lille, France
> 
> ______________________________________________
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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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