[R] any way to make it work faster (deleting rows that contain certain values)
Dimitri Liakhovitski
ld7631 at gmail.com
Wed Sep 23 15:42:24 CEST 2009
Chuck, thank you, but I am not sure I understood what you meant.
There are a lot of rows in "index" where at least 2 columns have equal
values and a lot of rows where column 1 has 2 and some other column
has 5 - same for 3 in column 1 and 6 in some other column, etc.
Thanks a lot for clarifying!
Dimitri
On Tue, Sep 22, 2009 at 5:36 PM, Charles C. Berry <cberry at tajo.ucsd.edu> wrote:
> 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.Liakhovitski at ninah.com
>>
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>>
>
> Charles C. Berry (858) 534-2098
> Dept of Family/Preventive
> Medicine
> E mailto:cberry at tajo.ucsd.edu UC San Diego
> http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
>
>
>
--
Dimitri Liakhovitski
Ninah.com
Dimitri.Liakhovitski at ninah.com
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