Linear Regression demo using R

linear_regression.R

# Setting up random matrix
data <- as.matrix(data.frame(Intercept = rep(1, 6),
                             a = c(3, 4, 5, 6, 7, 8),
                             b = c(1, 4, 3, 7, 10, 12),
                             c = c(6, 5, 1, 9, 18, 21)))

# Setting up the (perfect) linear relationship
preds <- 2 + (data[, 2] * 2) + (data[, 3] * 3) + (data[, 4] * 4)

# Plotting data to understand what we have
PerformanceAnalytics::chart.Correlation(data.frame(data, preds = preds))

# If you do not have PerformanceAnalytics package, use this instead
# plot(data.frame(data, preds = preds))

# Getting linear regression coefficients
coefficients <- solve(t(data) %*% data, tol = 1e-30) %*% t(data) %*% preds

# Predicting on data
data %*% coefficients