[R] Conditional Selection of Columns for Tables

Mark Hempelmann neo27 at rakers.de
Sat Jan 27 20:31:43 CET 2007

Dear Wizards -

	Thank you so much for your help. That was exactly what I was looking 
for. Now, I have been working on conditional selection of columns in a 
data frame. My goal is to calculate the total revenue per sales 
representative per status in a table. I have come to a complete stop:

Let's say, we have a data.frame called df with several columns and a
number of rows:

df <- data.frame( nr=101:110, letter=LETTERS[1:10],
name=c(rep("eenie",3), rep("meenie",2), rep("miney",4),
   "moe"), revenue=round(runif(10, min=100, max=1000),0),
status=round(runif(10,min=1, max=3),0) )

     nr letter   name revenue status
1  101      A  eenie     764      2
2  102      B  eenie     918      2
3  103      C  eenie     936      3
4  104      D meenie     770      2
5  105      E meenie     280      1
6  106      F  miney     172      2
7  107      G  miney     439      2
8  108      H  miney     607      1
9  109      I  miney     553      1
10 110      J    moe     322      2

where status means: 3=no deal, 2=pending, 1=good job.
now, we want the total revenue per sales representative per status in a

sum( subset(df, name=="eenie", select=revenue) )

gives the total of eenie without status, but I would like to have sthg like:

name   revenue
eenie  1000
meenie 2000...

name   revenue
eenie  100
meenie 200...

Are these flat contingency tables? How can I get the results without
much hazzle in one list/ table? i did read the ?ftable and what I was 
able to derive so far is:

flat.df <- ftable(df[c("name", "revenue", "status")])

but I am unable to further agglomerate the data. hmpf.
Good God, what would I do without my R-help forum?

Thank you again
Cheers and a relaxing weekend

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