# Set seed for reproducibility
set.seed(42)

# Randomly sample 70% of data indices for training set
train_indices <- sample(1:nrow(credit), nrow(credit)*0.7)

# Create training and testing datasets
train_data <- credit[train_indices, ]
test_data <- credit[-train_indices, ]

# Build logistic regression model
model2 <- glm(upgraded ~ purchases + extraCards, family = binomial, data = credit)

# Output of logistic regression model
summary(model2)