[R] Two problems
Peter Dalgaard BSA
p.dalgaard at biostat.ku.dk
Thu Apr 18 19:12:22 CEST 2002
"Ambrosini Alessandro" <klavan at tiscalinet.it> writes:
> Hello! Two questions:
> 1: I have to import a matrix of adjacency from a file of a software that is
> not R (for example "bloc notes" of Windows). The problem is that the matrix
> is not in the explicit form as
> 0 1 1
> 1 0 0
> 1 0 0
> but it is a scattered matrix where in each row there are two nodes that have
> a direct path.
> The matrix is
> a b
> a c
> b a
> c a
> For example, the first row exspress that node a and node b are connected by
> a direct line.
> Can R transform this matrix in the first matrix that I wrote ? Are there any
Use matrix indexing:
i <- matrix(c(1,2,
m <- matrix(0,3,3)
m[i] <- 1
> 2: Which is the max dimension of a matrix that R can use (1000X1000?,
> 500000X500000?)? What is the biggest dimension of a file that R can import?
It has to fit in available memory. On a 32 bit machine, you can only
address 4GB (and only if the OS allows), so in principle the workspace
holds 500 million double cells which would allow a 20000x20000 matrix.
However, you generally need to have room for several copies, so 5k x
5k sounds more realistic. I forget what current status is on 64-bit
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
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