20.19 Complexity Parameter

We can print a table of optimal prunings based on a complexity parameter using rpart::printcp(). The data is actually stored as model$cptable.

printcp(model)

## 
## Classification tree:
## rpart(formula=form, data=ds[tr, vars], model=TRUE)
## 
## Variables actually used in tree construction:
## [1] humidity_3pm    wind_gust_speed
## 
## Root node error: 32740/151934=0.21549
## 
## n= 151934 
## 
##         CP nsplit rel error  xerror      xstd
## 1 0.157575      0   1.00000 1.00000 0.0048951
## 2 0.033903      1   0.84243 0.84633 0.0045974
## 3 0.010000      3   0.77462 0.77850 0.0044485

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