Julia Arrays & Matrices
Master array operations and linear algebra in Julia.
Creating Arrays
# 1D array (vector)
v = [1, 2, 3, 4]
# 2D array (matrix)
m = [1 2; 3 4]
# Range
r = 1:5 # 1, 2, 3, 4, 5
# Array with type annotation
a = Float64[1, 2, 3]
Array Operations
# Element-wise operations
a = [1, 2, 3]
b = [4, 5, 6]
a + b # [5, 7, 9]
a .* b # [4, 10, 18] (element-wise multiplication)
# Dot product
using LinearAlgebra
dot(a, b) # 32
# Matrix multiplication
A = [1 2; 3 4]
B = [5 6; 7 8]
A * B
Indexing and Slicing
a = [10, 20, 30, 40, 50]
# Get element
a[1] # 10 (Julia is 1-indexed)
# Get range
a[2:4] # [20, 30, 40]
# Last element
a[end] # 50
# Matrix indexing
m = [1 2; 3 4]
m[1, 2] # 2
Array Comprehensions
# Simple comprehension
squares = [x^2 for x in 1:5] # [1, 4, 9, 16, 25]
# 2D comprehension
matrix = [i + j for i in 1:3, j in 1:4]
Common Array Functions
a = [3, 1, 4, 1, 5]
length(a) # 5
sum(a) # 14
maximum(a) # 5
sort(a) # [1, 1, 3, 4, 5]
# Reshape
reshape(1:9, 3, 3)