[R] Performance problems to fill up a dataframe

[Florian Jansen]

Dear Listmembers,

I'm trying to fill up a dataframe depending on an arbitrary list of 
references:

Here is my code, which works:

dat <- data.frame(c(60001,60001,60050,60050,60050),c(27,129,618,27,1579))
LR <- sort(unique(dat[,1]))
LC <- sort(unique(dat[,2]))
m <- as.data.frame(matrix(data=NA, nrow=length(LR), ncol=length(LC), 
dimnames=list(LR,LC)))

for(i in 1:nrow(dat)){
  m[as.character(dat[i,1]), as.character(dat[i,2])] <- 1
  }
m[is.na(m)] <- 0

Now I'm trying to prevent the loop, because it take ages for a list of 
20000 entries, but I run out of ideas.
Should I inflate my list beforehand and how? Can I adress the dataframe 
fields more effieciently?

Thanks for your help.


-- 
Dr. Florian Jansen
Geobotany & Nature Conservation
Institute of Botany and Landscape Ecology
Ernst-Moritz-Arndt-University
Grimmer Str. 88
17487 Greifswald
Germany
+49 (0)3834 86 4147