Thanks David, your suggestion works fine.....btw I have another
question......If I set (n,m) little bit large, say (n=20,m=10), R cannot
handle the large data frame generated through "expand.grid".....Is there
any way to increase R-memory so that I can tackle large data.frame in R
?????
regards
ritwik
>
> On Mar 23, 2012, at 2:53 AM, ritwi...@isical.ac.in wrote:
>
>> Dear Sir/Madam,
>>
>> I'm getting a problem with a R-code which converts a data frame to a
>> matrix.
>>
>> It first generate a (m^(n-m) * m) matrix A and then regenerate another
>> matrix B having less dimension than A which satisfy some condition.
>> Now I
>> wish to assign each row of B to a vector as individual.
>>
>> My problem is when I set any choice of (n,m) except m=1 it works
>> fine but
>> setting m=1 I got the error : Error in B[i, ] : incorrect number of
>> dimensions.
>>
>> Moreover if (n,m) is large (say, (20,8)) I got the error : Error:
>> cannot
>> allocate vector of size 3.0 Gb. I know this is due to large
>> dimension of
>> matrix A. How to solve this problem.
>>
>> My code is given below:
>>
>> **********************************************************************
>>
>> n=5
>> m=3
>> R=numeric(0)
>> # Generate all possible m-tuple ( variables having range 0 to n )
>> in a (
>> m^(n-m) * m ) matrix
>>
>> r = expand.grid(rep(list(0:(n-m)), m))
>>
>> write.table(r,file="test.txt",row.names=FALSE,col.names=FALSE)
>>
>> a= read.table(file="test.txt",sep="",header=FALSE)
>>
>> A= data.matrix(a)
>>
>> #.........................................................................................
>>
>> # Generate matrix whose rowsum = n-m
>>
>> meet.crit = apply(A, 1, function(.row) any((sum(.row)) == n-m)) #
>> criteron for being rowsum = n
>>
>> cbind(A, meet.crit) #
>> Checking rowsum = n for each row
>> -m
>> B=A[meet.crit,]
>
> At this point the default behavior of the "[" function is to return a
> vector rather than a matrix. You need to add drop=FALSE as an
> additional argument. Read the help page for ?"[".
>
> #
>> Generate matrix
>>
>> #.........................................................................................
>>
>>
>> for(i in 1:choose(n-1,m-1)){
>> R=B[i,]
>> }
>>
>> ***************************************************************************
>>
>> Can you please help me how to get rid of these errors. Thanking you in
>> advance.
>>
>> Regards
>>
>> Ritwik Bhattacharya
>>
>>
>> Senior Research Fellow
>> SQC & OR UNIT, KOLKATA
>> INDIAN STATISTICAL INSTITUTE
>
> --
>
> David Winsemius, MD
> West Hartford, CT
>
> This mail is scanned by Ironport
>
>
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