R: Lower and Upper Triangular Part of a Sparse Matrix

lower.tri {spam}

R Documentation

Lower and Upper Triangular Part of a Sparse Matrix

Description

Returns the lower or upper triangular structure or entries of a sparse matrix.

Usage

lower.tri(x, diag = FALSE)
upper.tri(x, diag = FALSE)

Arguments

`x`	a sparse matrix of class `spam`
`diag`	logical. Should the diagonal be included?

Details

Often not only the structure of the matrix is required but the entries as well. For compatibility, the default is only a structure consisting of ones (representing TRUEs). Setting the flag spam.getOption('trivalues') to TRUE, the function returns the actual values.

Examples

smat <- spam( c( 1,2,0,3,0,0,0,4,5),3)
upper.tri( smat)
upper.tri( smat, diag=TRUE)

spam.options( trivalues=TRUE)
upper.tri( smat)