R help - Jan 2003 - problem with as.data.frame.table

Dear all, 

I think that what I want is an as.data.frame.table-object, but see error
message below.

I have a data frame with one tree per row, diaclass tells if it is a small,
mid or large tree
> cpy.tradart[1:5, ]
  ObjektID diaclass
1 AX.Grb.1   bigdia
2 AX.Grb.1   middia
3 AX.Grb.1   middia
4 AX.Grb.1 smalldia
5 AX.Grb.1   middia
> 
I want a data frame telling no of trees per diameter class, per ObjektID
 
There are 107 ObjektID
> nlevels(cpy.tradart$ObjektID)
[1] 107
 
and  3 diaclass levels
> levels(cpy.tradart$diaclass)
[1] "bigdia"   "middia"   "smalldia"
 
I first split the data frame
> group <- split(cpy.tradart$diaclass, list(cpy.tradart[,
c("ObjektID",
"diaclass")])) # 
> 
and then sapply
> test <- sapply( group, function(x) sum(length(x)))
> 
> # This looks good
> test[1:5]
 AX.Grb.O.bigdia       S.1.bigdia S.1.ominv.bigdia      S.10.bigdia
S.11.bigdia 
               6                3                3               11
       5 
> 
> # But not each diaclass is represented in each ObjektID, because
> length(test)
[1] 313
> # is smaller than 3*107
and I cannot split up the names of each element of the vector "test".

# What I want is a data frame like this:

ObjectID    diaclass  Frequency
AX.Grb.1    smalldia      23
AX.Grb.1    middia        45
AX.Grb.1    bigdia         0
AX.Grb.2    smalldia       2
AX.Grb.2    middia         5
AX.Grb.2    bigdia        10
AX.Grb.3    smalldia       3
AX.Grb.3    middia        45
AX.Grb.3    bigdia         0

Note that there will be zeroes, but that information is lacking in
"test".

I have also tried:
> as.data.frame.table(cpy.tradart)
Error in as.table.default(x) : cannot coerce into a table



Could someone please give a hint.


Thanks in advance!!


Sincerely,
Tord



-----------------------------------------------------------------------
Tord Sn?ll
Avd. f v?xtekologi, Evolutionsbiologiskt centrum, Uppsala universitet
Dept. of Plant Ecology, Evolutionary Biology Centre, Uppsala University
Villav?gen 14			
SE-752 36 Uppsala, Sweden
Tel: 018-471 28 82 (int +46 18 471 28 82) (work)
Tel: 018-25 71 33 (int +46 18 25 71 33) (home)
Fax: 018-55 34 19 (int +46 18 55 34 19) (work)
E-mail: Tord.Snall at ebc.uu.se
Check this: http://www.vaxtbio.uu.se/resfold/snall.htm!
------------------------------------------------------------------------

Tord Snall <tord.snall at ebc.uu.se> writes:
> Dear all, 
> 
> I think that what I want is an as.data.frame.table-object, but see error
> message below.
(Haven't we been here before??)

There's no such thing as an as.data.frame.table-object.
as.data.frame.table turns table objects into data frames.
 
> I have a data frame with one tree per row, diaclass tells if it is a small,
> mid or large tree
> 
> > cpy.tradart[1:5, ]
>   ObjektID diaclass
> 1 AX.Grb.1   bigdia
> 2 AX.Grb.1   middia
> 3 AX.Grb.1   middia
> 4 AX.Grb.1 smalldia
> 5 AX.Grb.1   middia
> > 
> 
> I want a data frame telling no of trees per diameter class, per ObjektID
What's wrong with as.data.frame(table(ObjektID,diaclass)) then?


-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
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~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907