Subset a LazyMatrix by columns

Subsets a LazyMatrix object by columns, returning either a LazyColumn or a new LazyMatrix depending on the number of columns selected. Row subsetting is not yet supported.

Usage

# S4 method for class 'LazyMatrix,ANY,ANY,ANY'
x[i, j, ..., drop = TRUE]

Arguments

x

A LazyMatrix object.

i

Row index. Must be missing as row subsetting is not yet supported.

j

Column index. Either a single integer returning a LazyColumn, or a vector of integers returning a LazyMatrix.

...

Additional arguments (ignored).

drop

Logical. Currently ignored.

Value

A LazyColumn if a single column is selected, or a LazyMatrix if multiple columns are selected.

Examples

A <- Matrix::sparseMatrix(i = c(1,2,3), j = c(1,2,3), x = c(1,2,3))
lazy_m <- LazyMatrix(A, "sd", "mean")

# Single column → LazyColumn
lazy_col <- lazy_m[, 2]

# Multiple columns → LazyMatrix
lazy_subset <- lazy_m[, 1:3]