pbdBASE (version 0.1-1)

Extract: Extract or Replace Parts of a Distributed Matrix

Description

Operators to extract or replace parts of a distributed matrix.

Usage

x[i, j, ..., ICTXT]
  
  ## S3 method for class 'ddmatrix':
head(x, n = 6L, ...)
  ## S3 method for class 'ddmatrix':
tail(x, n = 6L, ...)

Arguments

x

numeric distributed matrix.

i, j

indices specifying elements to extract or replace. Indices can be numeric, character, empty, or NULL.

n

a single integer. If positive, size for the resulting object: number of elements for a vector (including lists), rows for a matrix or data frame or lines for a function. If negative, all but the n last/first number of elements of

...

additional arguments.

ICTXT

optional BLACS context number for output

Value

• Returns a distributed matrix.

Details

[ can be used to extract/replace for a distributed matrix exactly as you would with an ordinary matrix. The functions rely on reblocking across different BLACS contexts. If i is not empty, then the input distributed matrix will be redistributed along context 1, where extracting/deleting rows does not destroy block-cyclicality. Likewise, if j is not empty, then the input distributed matrix will be redistributed along context 2. When extraction is complete, the matrix will be redistributed across its input context.

See Also

BLACS, InitGrid

Examples

# Save code in a file "demo.r" and run with 2 processors by
# > mpiexec -np 2 Rscript demo.r

library(pbdBASE, quiet = TRUE)
init.grid()

# don't do this in production code
x <- matrix(1:9, 3)
x <- as.ddmatrix(x)

y <- x[, -1]
y <- head(y, 2)
print(y)

finalize()