[R] R Error : DATA to MATRIX
Petr PIKAL
petr.pikal at precheza.cz
Fri Mar 23 13:48:36 CET 2012
Hi
See in text.
>
> 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)
Above lines do not do any sensible things. r shall be same as a.
>
> 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
No error
>
> cbind(A, meet.crit) #
> Checking rowsum = n for each row
> -m
> B=A[meet.crit,] #
No error
> Generate matrix
>
>
#.........................................................................................
>
>
> for(i in 1:choose(n-1,m-1)){
> R=B[i,]
> }
No error. However in each cycle only ith row is added to R and therefore
only last row (in this case B[6,]) is added and stays in R. Either you
need to use
R <- c(R, B[i,])
in your construction or better as B is matrix
> class(B)
[1] "matrix"
you can transform it to vector easily by stripping dimensions.
R<-t(B)
> dim(R) <-NULL
> R
[1] 2 0 0 1 1 0 0 2 0 1 0 1 0 1 1 0 0 2
Regards
Petr
>
>
***************************************************************************
>
> 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
>
> Voice : +91 9051253944
>
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