# R's genuine historical airquality data; no network or CSV required
data("airquality", package = "datasets")
columns <- c("Ozone", "Temp", "Wind", "Solar.R")
complete <- na.omit(airquality[columns])
cat("Original daily records:", nrow(airquality), "\n")
cat("Complete rows for this analysis:", nrow(complete), "\n")
simple <- lm(Ozone ~ Temp, data = complete)
multiple <- lm(Ozone ~ Temp + Wind + Solar.R, data = complete)
cat("Simple temperature coefficient:", coef(simple)["Temp"], "\n")
cat("Adjusted temperature coefficient:", coef(multiple)["Temp"], "\n")
print(summary(multiple))
plot(fitted(multiple), resid(multiple), pch = 19,
     col = "#476E74", xlab = "Fitted ozone (ppb)",
     ylab = "Regression residual (ppb)", main = "Complete-case model diagnostics")
abline(h = 0, col = '#AE713A', lty = 2)