Question 2.1
Describe a situation or problem from your job, everyday life, current events, etc., for which a
classification model would be appropriate. List some (up to 5) predictors that you might use.
Question 2.2
The files credit_card_data.txt (without headers) and credit_card_data-headers.txt
(with headers) contain a dataset with 654 data points, 6 continuous and 4 binary predictor variables. It
has anonymized credit card applications with a binary response variable (last column) indicating if the
application was positive or negative. The dataset is the “Credit Approval Data Set” from the UCI Machine
Learning Repository (https://archive.ics.uci.edu/ml/datasets/Credit+Approval) without the categorical
variables and without data points that have missing values.
1. Using the support vector machine function ksvm contained in the R package kernlab, find a
good classifier for this data. Show the equation of your classifier, and how well it classifies the
data points in the full data set. (Don’t worry about test/validation data yet; we’ll cover that
topic soon.)
Notes on ksvm
• You can use scaled=TRUE to get ksvm to scale the data as part of calculating a
classifier.
• The term λ we used in the SVM lesson to trade off the two components of correctness
and margin is called C in ksvm. One of the challenges of this homework is to find a
value of C that works well; for many values of C, almost all predictions will be “yes” or
almost all predictions will be “no”.
• ksvm does not directly return the coefficients a0 and a1…am. Instead, you need to do
the last step of the calculation yourself. Here’s an example of the steps to take
(assuming your data is stored in a matrix called data): 1
# call ksvm. Vanilladot is a simple linear kernel.
model <- ksvm(data[,1:10],data[,11],type=”C-
svc”,kernel=”vanilladot”,C=100,scaled=TRUE)
# calculate a1…am
a <- colSums(model@xmatrix[[1]] * model@coef[[1]])
a
# calculate a0
a0 <- –model@b
a0
# see what the model predicts
pred <- predict(model,data[,1:10])
pred
1 I know I said I wouldn’t give you exact R code to copy, because I want you to learn for yourself. In general, that’s
definitely true – but in this case, because it’s your first R assignment and because the ksvm function leaves you in
the middle of a mathematical calculation that we haven’t gotten into in this course, I’m giving you the code.
