Plots for BenchmarkAggr

Generates plots for BenchmarkAggr, all assume that there are multiple, independent, tasks. Choices depending on the argument type:

• "mean" (default): Assumes there are at least two independent tasks. Plots the sample mean of the measure for all learners with error bars computed with the standard error of the mean.

• "box": Boxplots for each learner calculated over all tasks for a given measure.

• "fn": Plots post-hoc Friedman-Nemenyi by first calling BenchmarkAggr$friedman_posthoc and plotting significant pairs in coloured squares and leaving non-significant pairs blank, useful for simply visualising pair-wise comparisons.

• "cd": Critical difference plots (Demsar, 2006). Learners are drawn on the x-axis according to their average rank with the best performing on the left and decreasing performance going right. Any learners not connected by a horizontal bar are significantly different in performance. Critical differences are calculated as: $$CD = q_{\alpha} \sqrt{\left(\frac{k(k+1)}{6N}\right)}$$ Where \(q_\alpha\) is based on the studentized range statistic. See references for further details. It's recommended to crop white space using external tools, or function image_trim() from package magick.

Usage

# S3 method for BenchmarkAggr
autoplot(
  object,
  type = c("mean", "box", "fn", "cd"),
  meas = NULL,
  level = 0.95,
  p.value = 0.05,
  minimize = TRUE,
  test = "nem",
  baseline = NULL,
  style = 1L,
  ratio = 1/7,
  col = "red",
  friedman_global = TRUE,
  ...
)

Arguments

object

(BenchmarkAggr)
The benchmark aggregation object.

type

(character(1))
Type of plot, see description.

meas

(character(1))
Measure to plot, should be in obj$measures, can be NULL if only one measure is in obj.

level

(numeric(1))
Confidence level for error bars for type = "mean"

p.value

(numeric(1))
What value should be considered significant for type = "cd" and type = "fn".

minimize

(logical(1))
For type = "cd", indicates if the measure is optimally minimized. Default is TRUE.

test

(character(1)))
For type = "cd", critical differences are either computed between all learners (test = "nemenyi"), or to a baseline (test = "bd"). Bonferroni-Dunn usually yields higher power than Nemenyi as it only compares algorithms to one baseline. Default is "nemenyi".

baseline

(character(1))
For type = "cd" and test = "bd" a baseline learner to compare the other learners to, should be in $learners, if NULL then differences are compared to the best performing learner.

style

(integer(1))
For type = "cd" two ggplot styles are shipped with the package (style = 1 or style = 2), otherwise the data can be accessed via the returned ggplot.

ratio

(numeric(1))
For type = "cd" and style = 1, passed to ggplot2::coord_fixed(), useful for quickly specifying the aspect ratio of the plot, best used with ggsave().

col

(character(1))
For type = "fn", specifies color to fill significant tiles, default is "red".

friedman_global

(logical(1))
Should a friedman global test be performed fortype = "cd" and type = "fn"? If FALSE, a warning is issued in case the corresponding friedman posthoc test fails instead of an error. Default is TRUE (raises an error if global test fails).

...

ANY
Additional arguments, currently unused.

Value

The generated plot.

References

Demšar J (2006). “Statistical Comparisons of Classifiers over Multiple Data Sets.” Journal of Machine Learning Research, 7(1), 1-30. https://jmlr.org/papers/v7/demsar06a.html.

Examples

if (requireNamespaces(c("mlr3learners", "mlr3", "rpart", "xgboost"))) {
library(mlr3)
library(mlr3learners)
library(ggplot2)

set.seed(1)
task = tsks(c("iris", "sonar", "wine", "zoo"))
learns = lrns(c("classif.featureless", "classif.rpart", "classif.xgboost"))
bm = benchmark(benchmark_grid(task, learns, rsmp("cv", folds = 3)))
obj = as_benchmark_aggr(bm)

# mean and error bars
autoplot(obj, type = "mean", level = 0.95)

if (requireNamespace("PMCMRplus", quietly = TRUE)) {
  # critical differences
  autoplot(obj, type = "cd",style = 1)
  autoplot(obj, type = "cd",style = 2)

  # post-hoc friedman-nemenyi
  autoplot(obj, type = "fn")
}

}