These functions calculate the recall() of a measurement system for finding relevant documents compared to reference results (the truth regarding relevance). Highly related functions are precision() and f_meas().

## Usage

recall(data, ...)

# S3 method for data.frame
recall(
data,
truth,
estimate,
estimator = NULL,
na_rm = TRUE,
case_weights = NULL,
event_level = yardstick_event_level(),
...
)

recall_vec(
truth,
estimate,
estimator = NULL,
na_rm = TRUE,
case_weights = NULL,
event_level = yardstick_event_level(),
...
)

## Arguments

data

Either a data.frame containing the columns specified by the truth and estimate arguments, or a table/matrix where the true class results should be in the columns of the table.

...

Not currently used.

truth

The column identifier for the true class results (that is a factor). This should be an unquoted column name although this argument is passed by expression and supports quasiquotation (you can unquote column names). For _vec() functions, a factor vector.

estimate

The column identifier for the predicted class results (that is also factor). As with truth this can be specified different ways but the primary method is to use an unquoted variable name. For _vec() functions, a factor vector.

estimator

One of: "binary", "macro", "macro_weighted", or "micro" to specify the type of averaging to be done. "binary" is only relevant for the two class case. The other three are general methods for calculating multiclass metrics. The default will automatically choose "binary" or "macro" based on estimate.

na_rm

A logical value indicating whether NA values should be stripped before the computation proceeds.

case_weights

The optional column identifier for case weights. This should be an unquoted column name that evaluates to a numeric column in data. For _vec() functions, a numeric vector.

event_level

A single string. Either "first" or "second" to specify which level of truth to consider as the "event". This argument is only applicable when estimator = "binary". The default uses an internal helper that generally defaults to "first", however, if the deprecated global option yardstick.event_first is set, that will be used instead with a warning.

## Value

A tibble with columns .metric, .estimator, and .estimate and 1 row of values.

For grouped data frames, the number of rows returned will be the same as the number of groups.

For recall_vec(), a single numeric value (or NA).

## Details

The recall (aka sensitivity) is defined as the proportion of relevant results out of the number of samples which were actually relevant. When there are no relevant results, recall is not defined and a value of NA is returned.

When the denominator of the calculation is 0, recall is undefined. This happens when both # true_positive = 0 and # false_negative = 0 are true, which mean that there were no true events. When computing binary recall, a NA value will be returned with a warning. When computing multiclass recall, the individual NA values will be removed, and the computation will procede, with a warning.

## Relevant Level

There is no common convention on which factor level should automatically be considered the "event" or "positive" result when computing binary classification metrics. In yardstick, the default is to use the first level. To alter this, change the argument event_level to "second" to consider the last level of the factor the level of interest. For multiclass extensions involving one-vs-all comparisons (such as macro averaging), this option is ignored and the "one" level is always the relevant result.

## Multiclass

Macro, micro, and macro-weighted averaging is available for this metric. The default is to select macro averaging if a truth factor with more than 2 levels is provided. Otherwise, a standard binary calculation is done. See vignette("multiclass", "yardstick") for more information.

## Implementation

Suppose a 2x2 table with notation:

 Reference Predicted Relevant Irrelevant Relevant A B Irrelevant C D

The formulas used here are:

$$recall = A/(A+C)$$ $$precision = A/(A+B)$$ $$F_{meas} = (1+\beta^2) * precision * recall/((\beta^2 * precision)+recall)$$

See the references for discussions of the statistics.

## References

Buckland, M., & Gey, F. (1994). The relationship between Recall and Precision. Journal of the American Society for Information Science, 45(1), 12-19.

Powers, D. (2007). Evaluation: From Precision, Recall and F Factor to ROC, Informedness, Markedness and Correlation. Technical Report SIE-07-001, Flinders University

Other class metrics: accuracy(), bal_accuracy(), detection_prevalence(), f_meas(), j_index(), kap(), mcc(), npv(), ppv(), precision(), sens(), spec()

Other relevance metrics: f_meas(), precision()

Max Kuhn

## Examples

# Two class
data("two_class_example")
recall(two_class_example, truth, predicted)
#> # A tibble: 1 × 3
#>   .metric .estimator .estimate
#>   <chr>   <chr>          <dbl>
#> 1 recall  binary         0.880

# Multiclass
library(dplyr)
data(hpc_cv)

hpc_cv %>%
filter(Resample == "Fold01") %>%
recall(obs, pred)
#> # A tibble: 1 × 3
#>   .metric .estimator .estimate
#>   <chr>   <chr>          <dbl>
#> 1 recall  macro          0.548

# Groups are respected
hpc_cv %>%
group_by(Resample) %>%
recall(obs, pred)
#> # A tibble: 10 × 4
#>    Resample .metric .estimator .estimate
#>    <chr>    <chr>   <chr>          <dbl>
#>  1 Fold01   recall  macro          0.548
#>  2 Fold02   recall  macro          0.541
#>  3 Fold03   recall  macro          0.634
#>  4 Fold04   recall  macro          0.570
#>  5 Fold05   recall  macro          0.550
#>  6 Fold06   recall  macro          0.540
#>  7 Fold07   recall  macro          0.531
#>  8 Fold08   recall  macro          0.584
#>  9 Fold09   recall  macro          0.568
#> 10 Fold10   recall  macro          0.537

# Weighted macro averaging
hpc_cv %>%
group_by(Resample) %>%
recall(obs, pred, estimator = "macro_weighted")
#> # A tibble: 10 × 4
#>    Resample .metric .estimator     .estimate
#>    <chr>    <chr>   <chr>              <dbl>
#>  1 Fold01   recall  macro_weighted     0.726
#>  2 Fold02   recall  macro_weighted     0.712
#>  3 Fold03   recall  macro_weighted     0.758
#>  4 Fold04   recall  macro_weighted     0.712
#>  5 Fold05   recall  macro_weighted     0.712
#>  6 Fold06   recall  macro_weighted     0.697
#>  7 Fold07   recall  macro_weighted     0.675
#>  8 Fold08   recall  macro_weighted     0.721
#>  9 Fold09   recall  macro_weighted     0.673
#> 10 Fold10   recall  macro_weighted     0.699

# Vector version
recall_vec(
two_class_example$truth, two_class_example$predicted
)
#> [1] 0.879845

# Making Class2 the "relevant" level
recall_vec(
two_class_example$truth, two_class_example$predicted,
event_level = "second"
)
#> [1] 0.7933884