# ============================================================
# Matrices in R
# R Foundations — Rverse Analytics
# https://rverseanalytics.com/learn/matrices
# ============================================================

# Matrices in R - a 2D grid of one type
# 1. Fold a vector into rows and columns
m <- matrix(1:12, nrow = 3)
m
# 2. Shape and indexing: [row, column]
dim(m)
m[2, 3]
m[1, ]
m[, 2]
# 3. Maths is elementwise
m * 10
m + m
# 4. Whole-row and whole-column summaries
rowSums(m)
colMeans(m)
t(m)
# 5. Label rows and columns
rownames(m) <- c("a", "b", "c")
colnames(m) <- c("w", "x", "y", "z")
m["b", "y"]