R help - Oct 2009 - crosstabulation and unlist function

Hello R-users,

My toy example:
 aa<-c(1:5)
 bb<-c(NA,2,NA,4,5)
 cc<-c(1,2,NA,4,NA)
 dd<-c("A","B","B","A","C")
 df<-data.frame(aa,bb,cc,dd=as.factor(dd))
 table(unlist(df[,1:3]))

Can anyone point me to what function let's me do a crosstabulation between  
table(unlist(df[,1:3])) and df$dd?
I want to find out when dd==A (or B, or C) how many times do the values 1, 2
,3,..  appear in df[,1:3]?
Thank you very much!

 Eugen Pircalabelu

On Oct 12, 2009, at 2:36 PM, eugen pircalabelu wrote:
> Hello R-users,
>
> My toy example:
> aa<-c(1:5)
> bb<-c(NA,2,NA,4,5)
> cc<-c(1,2,NA,4,NA)
>
dd<-c("A","B","B","A","C")
> df<-data.frame(aa,bb,cc,dd=as.factor(dd))
> table(unlist(df[,1:3]))
>
> Can anyone point me to what function let's me do a crosstabulation  
> between   table(unlist(df[,1:3])) and df$dd?
> I want to find out when dd==A (or B, or C) how many times do the  
> values 1, 2 ,3,..  appear in df[,1:3]?
> Thank you very much!
One way would be to collect the row sums of those columns first, and  
then sum by index:

tapply(apply(df[,1:3],1,sum, na.rm=TRUE), df$dd, sum)
  A  B  C
14  9 10

-- 

David Winsemius, MD
Heritage Laboratories
West Hartford, CT