README.md

FFTrees

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The goal of FFTrees is to create and visualize fast-and-frugal decision trees (FFTs) from data with a binary outcome following the methods described in Phillips, Neth, Woike & Gaissmaier (2017).

Installation

You can install the released version of FFTrees from CRAN with:

install.packages("FFTrees")

And the development version from GitHub with:

# install.packages("devtools")
devtools::install_github("ndphillips/FFTrees", build_vignettes = TRUE)

Examples

library(FFTrees)
#> 
#>    O
#>   / \
#>  F   O
#>     / \
#>    F   Trees 1.5.3
#> 
#> Nathaniel.D.Phillips.is@gmail.com
#> FFTrees.guide() opens the guide.

Let’s create a fast-and-frugal tree predicting heart disease status (“Healthy” vs. “Diseased”) based on a heart.train dataset, and test it on heart.test a testing dataset.

Here are the first new rows and columns of heart.train, our training dataset. The key column is diagnosis, a logical column (TRUE and FALSE) which indicate, for each patient, whether or not they have heart disease. The heart.test dataset looks similar but with different cases (i.e.; patients)

knitr::kable(heart.train[1:7, 1:10])

| diagnosis | age | sex | cp | trestbps | chol | fbs | restecg | thalach | exang | | :-------- | --: | --: | :- | -------: | ---: | --: | :---------- | ------: | ----: | | FALSE | 44 | 0 | np | 108 | 141 | 0 | normal | 175 | 0 | | FALSE | 51 | 0 | np | 140 | 308 | 0 | hypertrophy | 142 | 0 | | FALSE | 52 | 1 | np | 138 | 223 | 0 | normal | 169 | 0 | | TRUE | 48 | 1 | aa | 110 | 229 | 0 | normal | 168 | 0 | | FALSE | 59 | 1 | aa | 140 | 221 | 0 | normal | 164 | 1 | | FALSE | 58 | 1 | np | 105 | 240 | 0 | hypertrophy | 154 | 1 | | FALSE | 41 | 0 | aa | 126 | 306 | 0 | normal | 163 | 0 |

Now let’s use FFTrees() to create a fast and frugal tree from the heart.train data and test their performance on heart.test

# Load package
library(FFTrees)

# Create an FFTrees object from the heartdisease data
heart.fft <- FFTrees(formula = diagnosis ~., 
                     data = heart.train,
                     data.test = heart.test, 
                     decision.labels = c("Healthy", "Disease"))
#> Setting goal = 'wacc'
#> Setting goal.chase = 'waccc'
#> Setting cost.outcomes = list(hi = 0, mi = 1, fa = 1, cr = 0)
#> Growing FFTs with ifan
#> Fitting other algorithms for comparison (disable with do.comp = FALSE) ...

# See the print method which shows aggregatge statistics
heart.fft
#> FFTrees 
#> - Trees: 7 fast-and-frugal trees predicting diagnosis
#> - Outcome costs: [hi = 0, mi = 1, fa = 1, cr = 0]
#> 
#> FFT #1: Definition
#> [1] If thal = {rd,fd}, decide Disease.
#> [2] If cp != {a}, decide Healthy.
#> [3] If ca <= 0, decide Healthy, otherwise, decide Disease.
#> 
#> FFT #1: Prediction Accuracy
#> Prediction Data: N = 153, Pos (+) = 73 (48%) 
#> 
#> |         | True + | True - |
#> |---------|--------|--------|
#> |Decide + | hi 64  | fa 19  | 83
#> |Decide - | mi 9   | cr 61  | 70
#> |---------|--------|--------|
#>             73       80       N = 153
#> 
#> acc  = 81.7%  ppv  = 77.1%  npv  = 87.1%
#> bacc = 82.0%  sens = 87.7%  spec = 76.2%
#> E(cost) = 0.183
#> 
#> FFT #1: Prediction Speed and Frugality
#> mcu = 1.73, pci = 0.87

# Plot the best tree applied to the test data
plot(heart.fft,
     data = "test",
     main = "Heart Disease")


# Compare results across algorithms in test data
heart.fft$competition$test
#>   algorithm   n hi fa mi cr      sens   spec    far       ppv       npv
#> 1   fftrees 153 64 19  9 61 0.8767123 0.7625 0.2375 0.7710843 0.8714286
#> 2        lr 153 55 13 18 67 0.7534247 0.8375 0.1625 0.8088235 0.7882353
#> 3      cart 153 50 19 23 61 0.6849315 0.7625 0.2375 0.7246377 0.7261905
#> 4        rf 153 58  6 15 74 0.7945205 0.9250 0.0750 0.9062500 0.8314607
#> 5       svm 153 55  7 18 73 0.7534247 0.9125 0.0875 0.8870968 0.8021978
#>         acc      bacc      cost cost_decisions cost_cues
#> 1 0.8169935 0.8196062 0.1830065      0.1830065         0
#> 2 0.7973856 0.7954623 0.2026144      0.2026144        NA
#> 3 0.7254902 0.7237158 0.2745098      0.2745098        NA
#> 4 0.8627451 0.8597603 0.1372549      0.1372549        NA
#> 5 0.8366013 0.8329623 0.1633987      0.1633987        NA

Because fast-and-frugal trees are so simple, you can create one ‘from words’ and apply it to data!

# Create your own custom FFT 'in words' and apply it to data

# Create my own fft
my.fft <- FFTrees(formula = diagnosis ~., 
                  data = heart.train,
                  data.test = heart.test, 
                  decision.labels = c("Healthy", "Disease"),
                  my.tree = "If sex = 1, predict Disease.
                             If age < 45, predict Healthy.
                             If thal = {fd, normal}, predict Disease. 
                             Otherwise, predict Healthy")
#> Setting goal = 'wacc'
#> Setting goal.chase = 'waccc'
#> Setting cost.outcomes = list(hi = 0, mi = 1, fa = 1, cr = 0)
#> Fitting other algorithms for comparison (disable with do.comp = FALSE) ...

# Plot my custom fft and see how it did
plot(my.fft,
     data = "test",
     main = "Custom FFT")

Citation

APA Citation

Phillips, Nathaniel D., Neth, Hansjoerg, Woike, Jan K., & Gaissmaier, W. (2017). FFTrees: A toolbox to create, visualize, and evaluate fast-and-frugal decision trees. Judgment and Decision Making, 12(4), 344-368.

We had a lot of fun creating FFTrees and hope you like it too! We have an article introducing the FFTrees package in the journal Judgment and Decision Making titled FFTrees: A toolbox to create, visualize,and evaluate fast-and-frugal decision trees. We encourage you to read the article to learn more about the history of FFTs and how the FFTrees package creates them.

If you use FFTrees in your work, please cite us and spread the word so we can continue developing the package

Here are some example publications that have used FFTrees:



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FFTrees documentation built on July 2, 2020, 2:13 a.m.