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
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