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: 29319/139059 = 0.21084
## 
## n= 139059 
## 
##         CP nsplit rel error  xerror      xstd
## 1 0.169617      0   1.00000 1.00000 0.0051881
## 2 0.023057      1   0.83038 0.83195 0.0048372
## 3 0.010000      3   0.78427 0.78529 0.0047276

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