# ============================================================
# Correlation: Pearson & Spearman
# Biostatistics in R — Rverse Analytics
# https://rverseanalytics.com/learn-biostatistics/correlation
# ============================================================

# Correlation - Pearson vs Spearman
# Built-in mtcars: weight vs fuel efficiency
cor(mtcars$wt, mtcars$mpg)
# Pearson correlation with a test and 95% CI
cor.test(mtcars$wt, mtcars$mpg)
# Spearman - rank based, for non-linear or non-normal data
cor.test(mtcars$wt, mtcars$mpg, method = "spearman")
# See the relationship
plot(mtcars$wt, mtcars$mpg, pch = 19, col = "#17a2b8", xlab = "Weight", ylab = "MPG")