Как я могу извлечь ошибку обучения из kernlab?

Question

Следующий код:

portuguese_scores = read.table("https://raw.githubusercontent.com/JimGorman17/Datasets/master/student-por.csv",sep=";",header=TRUE) 
portuguese_scores <- portuguese_scores[,!names(portuguese_scores) %in% c("school", "age", "G1", "G2")] 
median_score <- summary(portuguese_scores$G3)['Median'] 
portuguese_scores$score_gte_than_median <- as.factor(median_score<=portuguese_scores$G3) 
portuguese_scores <- portuguese_scores[,!names(portuguese_scores) %in% c("G3")] 

set.seed(123) 

train_sample <- sample(nrow(portuguese_scores), .9 * nrow(portuguese_scores)) 
port_train <- portuguese_scores[train_sample,] 
port_test <- portuguese_scores[-train_sample,] 

library(kernlab) 
median_classifier <- ksvm(score_gte_than_median ~ ., data=port_train, kernel="vanilladot") 
median_classifier 

Формирует следующий вывод:

Support Vector Machine object of class "ksvm" 

SV type: C-svc (classification) 
parameter : cost C = 1 

Linear (vanilla) kernel function. 

Number of Support Vectors : 320 

Objective Function Value : -300.32 
Training error : 0.208904 

Как я могу извлечь значение 'ошибки' Training в переменную?

Answer 1

Попробуйте

median_classifier@error 
[1] 0.2089041 

Это S4 объект. См. Документацию в слотах ksvm-class. ?'ksvm-class'