Perform the following steps to find highly correlated attributes:

1. Remove the features that are not coded in numeric characters:

        > new_train = trainset[,! names(churnTrain) %in% c("churn",
        "international_plan", "voice_mail_plan")]

2. Then, you can obtain the correlation of each attribute:

        >cor_mat = cor(new_train)  

3. Next, we use findCorrelation to search for highly correlated attributes with a cut off equal to 0.75:

        > highlyCorrelated = findCorrelation(cor_mat, cutoff=0.75) 

4. We then obtain the name of highly correlated attributes:

        > names(new_train)[highlyCorrelated]
        Output
        [1] "total_intl_minutes"  "total_day_charge"   
        "total_eve_minutes"   "total_night_minutes"