[R] How to obtain a cross tab count of unique values

[Sarah Goslee]

Sure: tell R you want unique rows.

> mydf <- data.frame(PROJECT=c("A","A","A","B","B","C","C"), PARKNAME=c("PRK A", "PRK B", "PRK A", "PRK C", "PRK A", "PRK B", "PRK D"), stringsAsFactors=FALSE)
> mydf
  PROJECT PARKNAME
1       A    PRK A
2       A    PRK B
3       A    PRK A
4       B    PRK C
5       B    PRK A
6       C    PRK B
7       C    PRK D

> mydf.unique <- unique(mydf)
> table(mydf.unique$PROJECT)

A B C
2 2 2

Please provide reproducible data yourself in the future.

Sarah

On Tue, Mar 31, 2015 at 3:51 PM, Walter Anderson <wandrson01 at gmail.com> wrote:
> I have a data frame that shows all of the parks (including duplicates)
> that are impacted by a projects 'footprint':
>
> PROJECT PARKNAME
> A       PRK A
> A       PRK B
> A       PRK A
> B       PRK C
> B       PRK A
> C       PRK B
> C       PRK D
> ...
>
> What I need is a cross tabulation that shows me the number of unique
> parks for each project.  If I using the standard table(df$PROJECT) it
> reports:
>
> A 3
> B 2
> C 2
> ...
>
> where I need it to ignore duplicates and report:
>
> A 2
> B 2
> C 2
> ...
>
> Anyone have any suggestions on how to do this within the R paradigm?
>
> Walter Anderson

-- 
Sarah Goslee
http://www.functionaldiversity.org