Takes a base-learner and extracts information.

```
# S3 method for blg
extract(
object,
what = c("design", "penalty", "index"),
asmatrix = FALSE,
expand = FALSE,
...
)
```

object

a base-learner

what

a character specifying the quantities to extract. This can be a subset of "design" (default; design matrix), "penalty" (penalty matrix) and "index" (index of ties used to expand the design matrix)

asmatrix

a logical indicating whether the the returned matrix should be
coerced to a matrix (default) or if the returned object stays as it is
(i.e., potentially a sparse matrix). This option is only applicable if `extract`

returns matrices, i.e., `what = "design"`

or `what = "penalty"`

.

expand

a logical indicating whether the design matrix should be expanded
(default: `FALSE`

). This is useful if ties were taken into account either manually
(via argument `index`

in a base-learner) or automatically for data sets with many
observations. `expand = TRUE`

is equivalent to `extract(B)[extract(B, what = "index"),]`

for a base-learner `B`

.

...

currently not used

`extract`

for the `extract`

function
of the package `mboost`

.