This package can be used to conduct post hoc analyses of resampling results generated by models.
For example, if two models are evaluated with the root mean squared error (RMSE) using 10-fold cross-validation, there are 10 paired statistics. These can be used to make comparisons between models without involving a test set.
There is a rich literature on the analysis of model resampling results such as McLachlan’s Discriminant Analysis and Statistical Pattern Recognition and the references therein. This package follows the spirit of Benavoli et al (2017).
tidyposterior uses Bayesian generalized linear models for this purpose
and can be considered an upgraded version of the
caret::resamples()
function. The package works with
rsample objects natively but any
results in a data frame can be used.
See Chapter 11 of Tidy Models with R for examples and more details.
You can install the released version of tidyposterior from CRAN with:
install.packages("tidyposterior")And the development version from GitHub with:
# install.packages("pak")
pak::pak("tidymodels/tidyposterior")To illustrate, here are some example objects using 10-fold cross-validation for a simple two-class problem:
library(tidymodels)
#> ── Attaching packages ────────────────────────────────────── tidymodels 1.1.0 ──
#> ✔ broom 1.0.5 ✔ recipes 1.0.8
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#> ✔ infer 1.0.4 ✔ tune 1.1.2
#> ✔ modeldata 1.2.0 ✔ workflows 1.1.3
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#> ✖ purrr::discard() masks scales::discard()
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#> • Search for functions across packages at https://www.tidymodels.org/find/
library(tidyposterior)
data(two_class_dat, package = "modeldata")
set.seed(100)
folds <- vfold_cv(two_class_dat)We can define two different models (for simplicity, with no tuning parameters).
logistic_reg_glm_spec <-
logistic_reg() %>%
set_engine('glm')
mars_earth_spec <-
mars(prod_degree = 1) %>%
set_engine('earth') %>%
set_mode('classification')For tidymodels, the [tune::fit_resamples()] function can be used to estimate performance for each model/resample:
rs_ctrl <- control_resamples(save_workflow = TRUE)
logistic_reg_glm_res <-
logistic_reg_glm_spec %>%
fit_resamples(Class ~ ., resamples = folds, control = rs_ctrl)
mars_earth_res <-
mars_earth_spec %>%
fit_resamples(Class ~ ., resamples = folds, control = rs_ctrl)From these, there are several ways to pass the results to the
perf_mod() function. The most general approach is to have a data frame
with the resampling labels (i.e., one or more id columns) as well as
columns for each model that you would like to compare.
For the model results above, [tune::collect_metrics()] can be used along with some basic data manipulation steps:
logistic_roc <-
collect_metrics(logistic_reg_glm_res, summarize = FALSE) %>%
dplyr::filter(.metric == "roc_auc") %>%
dplyr::select(id, logistic = .estimate)
mars_roc <-
collect_metrics(mars_earth_res, summarize = FALSE) %>%
dplyr::filter(.metric == "roc_auc") %>%
dplyr::select(id, mars = .estimate)
resamples_df <- full_join(logistic_roc, mars_roc, by = "id")
resamples_df
#> # A tibble: 10 × 3
#> id logistic mars
#> <chr> <dbl> <dbl>
#> 1 Fold01 0.856 0.845
#> 2 Fold02 0.933 0.951
#> 3 Fold03 0.934 0.937
#> 4 Fold04 0.864 0.858
#> 5 Fold05 0.847 0.854
#> 6 Fold06 0.911 0.840
#> 7 Fold07 0.867 0.858
#> 8 Fold08 0.886 0.876
#> 9 Fold09 0.898 0.898
#> 10 Fold10 0.906 0.894We can then give this directly to perf_mod():
set.seed(101)
roc_model_via_df <- perf_mod(resamples_df, iter = 2000)
#>
#> SAMPLING FOR MODEL 'continuous' NOW (CHAIN 1).
#> Chain 1:
#> Chain 1: Gradient evaluation took 0.000216 seconds
#> Chain 1: 1000 transitions using 10 leapfrog steps per transition would take 2.16 seconds.
#> Chain 1: Adjust your expectations accordingly!
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#> Chain 1: 0.433 seconds (Total)
#> Chain 1:
#>
#> SAMPLING FOR MODEL 'continuous' NOW (CHAIN 2).
#> Chain 2:
#> Chain 2: Gradient evaluation took 5e-06 seconds
#> Chain 2: 1000 transitions using 10 leapfrog steps per transition would take 0.05 seconds.
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#> Chain 2:
#>
#> SAMPLING FOR MODEL 'continuous' NOW (CHAIN 3).
#> Chain 3:
#> Chain 3: Gradient evaluation took 6e-06 seconds
#> Chain 3: 1000 transitions using 10 leapfrog steps per transition would take 0.06 seconds.
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#> Chain 3:
#>
#> SAMPLING FOR MODEL 'continuous' NOW (CHAIN 4).
#> Chain 4:
#> Chain 4: Gradient evaluation took 4e-06 seconds
#> Chain 4: 1000 transitions using 10 leapfrog steps per transition would take 0.04 seconds.
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#> Chain 4:From this, the posterior distributions for each model can be obtained
from the tidy() method:
roc_model_via_df %>%
tidy() %>%
ggplot(aes(x = posterior)) +
geom_histogram(bins = 40, col = "blue", fill = "blue", alpha = .4) +
facet_wrap(~ model, ncol = 1) +
xlab("Area Under the ROC Curve")
See contrast_models() for how to analyze these distributions
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