matrix definition
rectangular array of numbers
dimension of matrix
number of rows times number of columns
matrix numbers x by y is which
rows by columns
Funny R symbol
All matrices of specific dimension
Matrix elements
entries inside of matrix
vector defined as
An n x 1 matrix
4 dimensional vector means
4 x 1 matrix (vector)
y sub(i) of vector
ith element
indexed vector types
0 or 1 like arrays in programming languages
upper case letters in linear algerbra
Matrix
lower case letters in linear algerbra
vectors
when can you add 2 matrices
when they have the same dimension
scalar in linear algerbra
single number
divide by a scalar
type 1/ x and multiply
multiply a x b against c x d, size of result
a x d
if a b multiply c d, what must b and c be
b must equal c
transpose [1 2 , 3 4]
[1 3,2 4]
identity
matrix with diagonal 1
inverse
matrix to make identity
