the elements are arranged in a two-dimensional rectangular layout

elements are the same atomic types

index starts from 1

M <- matrix(c(3:14), nrow = 4, byrow = TRUE) # elements are arranged by row
print(M)

N <- matrix(c(3:14), nrow = 4, byrow = FALSE) # elements are arranged by column
print(N)

rownames = c("row1", "row2", "row3", "row4")
colnames = c("col1", "col2", "col3")
P <- matrix(c(3:14), nrow = 4, byrow = TRUE, dimnames = list(rownames, colnames))
print(P)
		

rownames = c("row1", "row2", "row3", "row4")
colnames = c("col1", "col2", "col3")

P <- matrix(c(3:14), nrow = 4, byrow = TRUE, dimnames = list(rownames, colnames))
print(P)

print(P[1, 2]) # 4, first row, second column
print(P[1, ]) # first row
print(P[, 2]) # second column
		

M = matrix(1:12, nrow = 4)
print(M)

N = matrix(seq(2, 24, by = 2), nrow = 4)
print(N)

print(M+N) # addition
print(N-M) # substraction
print(M*N) # multiplication, elementwise
print(M/N) # division, elementwise

print(dim(M)) # dimension

print(M %*% t(N)) # matrix multiplication
		

Matrix Algebra