On Tue, 22 Sep 2009, Dimitri Liakhovitski wrote:
Hello, dear R'ers,
index<-expand.grid(1:7,1:4,1:4,1:4,1:4,1:4,1:4,1:4,1:4,1:4,1:4)
In this case, dim(index) is 7,340,032 (!) and 11.
I realize it's huge.
Then, I am trying to get rid of the undesired combinations of columns.
They should not contain identical values in any 2 columns.
Right, but you have only four values in each of columns 2:11.
And none of them can be identical.
There are exactly
choose(4,10)
rows that satisfy that constraint for columns 2:11.
The rows of your result are easily enumerated by hand. ;-)
HTH,
Chuck
Also if column 1 has a value of 5, there should be no 2 in any other column,
if column 1 has a value of 6, there should be no 3 in any other column, and
column 1 has a value of 7, there should be no 4 in any other column.
I worte a generic script to achieve that (below).
However, I was wondering if it's possible to make it any faster - it
looks like with that huge index it's going to take me days...
Thanks a lot for any suggestion!
Dimitri
index<-expand.grid(1:7,1:4,1:4,1:4,1:4,1:4,1:4,1:4,1:4,1:4,1:4)
bad.pairs<-matrix(c(1,1,2,2,3,3,4,4,5,2,6,3,7,4),nrow=7,ncol=2,byrow=T)
for(i in 1:ncol(index)){ # looping through columns of the "index"
for(pair in 1:nrow(bad.pairs)){ # looping through rows of "bad.pairs"
keep<-sapply(1:nrow(index), function(x){
temp<-(index[[x,i]]==bad.pairs[pair,1]) &
(any(index[x,-i]==bad.pairs[pair,2]))
return(temp)
})
index<-index[!keep,]
}
}
--
Dimitri Liakhovitski
Ninah.com
dimitri.liakhovit...@ninah.com
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Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:cbe...@tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
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