18.6 Decision Trees

20210103

Representation	Method	Measure
Tree	Recursive Partitioning	Information Gain

To build a decision tree we typically use rpart::rpart().

mtype <- "rpart"
mdesc <- "decision tree"

ds %>%
  select(all_of(vars)) %>%
  slice(tr) %>%
  rpart(form, ., method="class", control=rpart.control(maxdepth=3)) %T>%
  print() ->
model

## n= 123722 
## 
## node), split, n, loss, yval, (yprob)
##       * denotes terminal node
## 
##  1) root 123722 25822 No (0.7912902 0.2087098)  
##    2) humidity_3pm< 72.5 105610 14774 No (0.8601079 0.1398921) *
##    3) humidity_3pm>=72.5 18112  7064 Yes (0.3900177 0.6099823)  
##      6) humidity_3pm< 82.5 9469  4412 No (0.5340585 0.4659415)  
##       12) rainfall< 0.85 5291  1909 No (0.6391986 0.3608014) *
##       13) rainfall>=0.85 4178  1675 Yes (0.4009095 0.5990905) *
##      7) humidity_3pm>=82.5 8643  2007 Yes (0.2322110 0.7677890) *

Chapter 21 covers decision trees in detail whilst Chapter 14 uses decision trees as the model builder to demonstrate the model template. Examples of decision tree induction are available through the rain, iris, and pyiris packages from MLHub.

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