This function computes metrics from tuning results. The arguments and
output formats are closely related to those from `collect_metrics()`

, but
this function additionally takes a `metrics`

argument with a
metric set for new metrics to compute. This
allows for computing new performance metrics without requiring users to
re-evaluate models against resamples.

Note that the control option `save_pred = TRUE`

must
have been supplied when generating `x`

.

## Usage

```
compute_metrics(x, metrics, summarize, event_level, ...)
# Default S3 method
compute_metrics(x, metrics, summarize = TRUE, event_level = "first", ...)
# S3 method for class 'tune_results'
compute_metrics(x, metrics, ..., summarize = TRUE, event_level = "first")
```

## Arguments

- x
The results of a tuning function like

`tune_grid()`

or`fit_resamples()`

, generated with the control option`save_pred = TRUE`

.- metrics
A metric set of new metrics to compute. See the "Details" section below for more information.

- summarize
A single logical value indicating whether metrics should be summarized over resamples (

`TRUE`

) or return the values for each individual resample. See`collect_metrics()`

for more details on how metrics are summarized.- event_level
A single string containing either

`"first"`

or`"second"`

. This argument is passed on to yardstick metric functions when any type of class prediction is made, and specifies which level of the outcome is considered the "event".- ...
Not currently used.

## Value

A tibble. See `collect_metrics()`

for more details on the return value.

## Details

Each metric in the set supplied to the `metrics`

argument must have a metric
type (usually `"numeric"`

, `"class"`

, or `"prob"`

) that matches some metric
evaluated when generating `x`

. e.g. For example, if `x`

was generated with
only hard `"class"`

metrics, this function can't compute metrics that take in
class probabilities (`"prob"`

.) By default, the tuning functions used to
generate `x`

compute metrics of all needed types.

## Examples

```
# load needed packages:
library(parsnip)
library(rsample)
library(yardstick)
# evaluate a linear regression against resamples.
# note that we pass `save_pred = TRUE`:
res <-
fit_resamples(
linear_reg(),
mpg ~ cyl + hp,
bootstraps(mtcars, 5),
control = control_grid(save_pred = TRUE)
)
# to return the metrics supplied to `fit_resamples()`:
collect_metrics(res)
#> # A tibble: 2 × 6
#> .metric .estimator mean n std_err .config
#> <chr> <chr> <dbl> <int> <dbl> <chr>
#> 1 rmse standard 3.21 5 0.363 Preprocessor1_Model1
#> 2 rsq standard 0.732 5 0.0495 Preprocessor1_Model1
# to compute new metrics:
compute_metrics(res, metric_set(mae))
#> # A tibble: 1 × 6
#> .metric .estimator mean n std_err .config
#> <chr> <chr> <dbl> <int> <dbl> <chr>
#> 1 mae standard 2.57 5 0.347 Preprocessor1_Model1
# if `metrics` is the same as that passed to `fit_resamples()`,
# then `collect_metrics()` and `compute_metrics()` give the same
# output, though `compute_metrics()` is quite a bit slower:
all.equal(
collect_metrics(res),
compute_metrics(res, metric_set(rmse, rsq))
)
#> [1] TRUE
```