sparklyr (version 1.8.5)

ml_metrics_multiclass: Extracts metrics from a fitted table

Description

The function works best when passed a `tbl_spark` created by `ml_predict()`. The output `tbl_spark` will contain the correct variable types and format that the given Spark model "evaluator" expects.

Usage

ml_metrics_multiclass(
  x,
  truth = label,
  estimate = prediction,
  metrics = c("accuracy"),
  beta = NULL,
  ...
)

Arguments

x

A `tbl_spark` containing the estimate (prediction) and the truth (value of what actually happened)

truth

The name of the column from `x` with an integer field containing an the indexed value for each outcome . The `ml_predict()` function will create a new field named `label` which contains the expected type and values. `truth` defaults to `label`.

estimate

The name of the column from `x` that contains the prediction. Defaults to `prediction`, since its type and indexed values will match `truth`.

metrics

A character vector with the metrics to calculate. For multiclass models the possible values are: `acurracy`, `f_meas` (F-score), `recall` and `precision`. This function translates the argument into an acceptable Spark parameter. If no translation is found, then the raw value of the argument is passed to Spark. This makes it possible to request a metric that is not listed here but, depending on version, it is available in Spark. Other metrics form multi-class models are: `weightedTruePositiveRate`, `weightedFalsePositiveRate`, `weightedFMeasure`, `truePositiveRateByLabel`, `falsePositiveRateByLabel`, `precisionByLabel`, `recallByLabel`, `fMeasureByLabel`, `logLoss`, `hammingLoss`

beta

Numerical value used for precision and recall. Defaults to NULL, but if the Spark session's verion is 3.0 and above, then NULL is changed to 1, unless something different is supplied in this argument.

...

Optional arguments; currently unused.

Details

The `ml_metrics` family of functions implement Spark's `evaluate` closer to how the `yardstick` package works. The functions expect a table containing the truth and estimate, and return a `tibble` with the results. The `tibble` has the same format and variable names as the output of the `yardstick` functions.

Examples

if (FALSE) {
sc <- spark_connect("local")
tbl_iris <- copy_to(sc, iris)
iris_split <- sdf_random_split(tbl_iris, training = 0.5, test = 0.5)
model <- ml_random_forest(iris_split$training, "Species ~ .")
tbl_predictions <- ml_predict(model, iris_split$test)

ml_metrics_multiclass(tbl_predictions)

# Request different metrics
ml_metrics_multiclass(tbl_predictions, metrics = c("recall", "precision"))

# Request metrics not translated by the function, but valid in Spark
ml_metrics_multiclass(tbl_predictions, metrics = c("logLoss", "hammingLoss"))
}