summary.rpart: Summarize a Fitted Rpart Object

Description Usage Arguments Details See Also Examples

View source: R/summary.rpart.R

Description

Returns a detailed listing of a fitted rpart object.

Usage

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## S3 method for class 'rpart'
summary(object, cp = 0, digits = getOption("digits"), file, ...)

Arguments

object

fitted model object of class "rpart". This is assumed to be the result of some function that produces an object with the same named components as that returned by the rpart function.

digits

Number of significant digits to be used in the result.

cp

trim nodes with a complexity of less than cp from the listing.

file

write the output to a given file name. (Full listings of a tree are often quite long).

...

arguments to be passed to or from other methods.

Details

This function is a method for the generic function summary for class "rpart". It can be invoked by calling summary for an object of the appropriate class, or directly by calling summary.rpart regardless of the class of the object.

It prints the call, the table shown by printcp, the variable importance (summing to 100) and details for each node (the details depending on the type of tree).

See Also

summary, rpart.object, printcp.

Examples

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## a regression tree
z.auto <- rpart(Mileage ~ Weight, car.test.frame)
summary(z.auto)

## a classification tree with multiple variables and surrogate splits.
summary(rpart(Kyphosis ~ Age + Number + Start, data = kyphosis))

Example output

Call:
rpart(formula = Mileage ~ Weight, data = car.test.frame)
  n= 60 

          CP nsplit rel error    xerror       xstd
1 0.59534912      0 1.0000000 1.0682996 0.18130210
2 0.13452819      1 0.4046509 0.5454953 0.10472257
3 0.01282843      2 0.2701227 0.4138966 0.07922561
4 0.01000000      3 0.2572943 0.4026472 0.07054789

Variable importance
Weight 
   100 

Node number 1: 60 observations,    complexity param=0.5953491
  mean=24.58333, MSE=22.57639 
  left son=2 (45 obs) right son=3 (15 obs)
  Primary splits:
      Weight < 2567.5 to the right, improve=0.5953491, (0 missing)

Node number 2: 45 observations,    complexity param=0.1345282
  mean=22.46667, MSE=8.026667 
  left son=4 (22 obs) right son=5 (23 obs)
  Primary splits:
      Weight < 3087.5 to the right, improve=0.5045118, (0 missing)

Node number 3: 15 observations
  mean=30.93333, MSE=12.46222 

Node number 4: 22 observations
  mean=20.40909, MSE=2.78719 

Node number 5: 23 observations,    complexity param=0.01282843
  mean=24.43478, MSE=5.115312 
  left son=10 (15 obs) right son=11 (8 obs)
  Primary splits:
      Weight < 2747.5 to the right, improve=0.1476996, (0 missing)

Node number 10: 15 observations
  mean=23.8, MSE=4.026667 

Node number 11: 8 observations
  mean=25.625, MSE=4.984375 

Call:
rpart(formula = Kyphosis ~ Age + Number + Start, data = kyphosis)
  n= 81 

          CP nsplit rel error   xerror      xstd
1 0.17647059      0 1.0000000 1.000000 0.2155872
2 0.01960784      1 0.8235294 1.117647 0.2243268
3 0.01000000      4 0.7647059 1.176471 0.2282908

Variable importance
 Start    Age Number 
    64     24     12 

Node number 1: 81 observations,    complexity param=0.1764706
  predicted class=absent   expected loss=0.2098765  P(node) =1
    class counts:    64    17
   probabilities: 0.790 0.210 
  left son=2 (62 obs) right son=3 (19 obs)
  Primary splits:
      Start  < 8.5  to the right, improve=6.762330, (0 missing)
      Number < 5.5  to the left,  improve=2.866795, (0 missing)
      Age    < 39.5 to the left,  improve=2.250212, (0 missing)
  Surrogate splits:
      Number < 6.5  to the left,  agree=0.802, adj=0.158, (0 split)

Node number 2: 62 observations,    complexity param=0.01960784
  predicted class=absent   expected loss=0.09677419  P(node) =0.7654321
    class counts:    56     6
   probabilities: 0.903 0.097 
  left son=4 (29 obs) right son=5 (33 obs)
  Primary splits:
      Start  < 14.5 to the right, improve=1.0205280, (0 missing)
      Age    < 55   to the left,  improve=0.6848635, (0 missing)
      Number < 4.5  to the left,  improve=0.2975332, (0 missing)
  Surrogate splits:
      Number < 3.5  to the left,  agree=0.645, adj=0.241, (0 split)
      Age    < 16   to the left,  agree=0.597, adj=0.138, (0 split)

Node number 3: 19 observations
  predicted class=present  expected loss=0.4210526  P(node) =0.2345679
    class counts:     8    11
   probabilities: 0.421 0.579 

Node number 4: 29 observations
  predicted class=absent   expected loss=0  P(node) =0.3580247
    class counts:    29     0
   probabilities: 1.000 0.000 

Node number 5: 33 observations,    complexity param=0.01960784
  predicted class=absent   expected loss=0.1818182  P(node) =0.4074074
    class counts:    27     6
   probabilities: 0.818 0.182 
  left son=10 (12 obs) right son=11 (21 obs)
  Primary splits:
      Age    < 55   to the left,  improve=1.2467530, (0 missing)
      Start  < 12.5 to the right, improve=0.2887701, (0 missing)
      Number < 3.5  to the right, improve=0.1753247, (0 missing)
  Surrogate splits:
      Start  < 9.5  to the left,  agree=0.758, adj=0.333, (0 split)
      Number < 5.5  to the right, agree=0.697, adj=0.167, (0 split)

Node number 10: 12 observations
  predicted class=absent   expected loss=0  P(node) =0.1481481
    class counts:    12     0
   probabilities: 1.000 0.000 

Node number 11: 21 observations,    complexity param=0.01960784
  predicted class=absent   expected loss=0.2857143  P(node) =0.2592593
    class counts:    15     6
   probabilities: 0.714 0.286 
  left son=22 (14 obs) right son=23 (7 obs)
  Primary splits:
      Age    < 111  to the right, improve=1.71428600, (0 missing)
      Start  < 12.5 to the right, improve=0.79365080, (0 missing)
      Number < 3.5  to the right, improve=0.07142857, (0 missing)

Node number 22: 14 observations
  predicted class=absent   expected loss=0.1428571  P(node) =0.1728395
    class counts:    12     2
   probabilities: 0.857 0.143 

Node number 23: 7 observations
  predicted class=present  expected loss=0.4285714  P(node) =0.08641975
    class counts:     3     4
   probabilities: 0.429 0.571 

rpart documentation built on May 1, 2019, 11:16 p.m.