# Matlab Cheat Sheet

## Defining Matrices

Row vector x=[1 2 3]
Column vector x=[1 2 3]'
Matrix

A = [1 2; 3 4]

or

A=[1 2

3 4]

Transpose - use the apostrophe B = A'
Multiplication D = A*B

## Ranges

By integers from 0 to N x=0:N
By steps of .1 x=0:.1:N
Assign part of a matrix E(3:4,1:2) = A
Assign an entire column of a matrix F(:,1) = x'

## Sizes

Size of a matrix [m,n] = size(A)
Length of a vector n = length(x)

## Special Functions

Trig functions

sin(x)

cos(x)

etc.

Zero matrix

N x N zero matrix

M x N zero matrix

zeros(N)

zeros(M,N)

Identity matrix eye(N)

Random matrix

N x N random matrix with entries between 0 and 1

M x N random matrix

rand(N)

rand(M,N)

## Plotting

2-D plot with abscissae in x, ordinates in y plot(x,y)
2-D plot of sin(x) plot(x,sin(x))
2-D plot of sin(x) using green diamonds to indicate points plot(x,sin(x),'gd')

Save current variables in "matlab.mat" save
Save current variables in "myfile.mat" save myfile

## Eigenvalues

Eigenvalues of a matrix eig(A)
Eigenvalues and eigenvectors of A [evec,eval]=eig(A)
QR decomposition of a matrix [Q,R] = qr(A)

## Gauss elimination

LU decomposition of a matrix [L,U] = lu(A)
LU with a permutation matrix [L,U,P] = lu(A)
Cholesky decomposition of a symmetric matrix R = chol(A)
Solve Ax = b for x x = A\b

The "final exam" for this course will take place at 8:00 AM on Tuesday, 12 December. This will be an ordinary 50 minute test. It will be comprehensive, but weighted toward the latter half of the semester. As always, paper notes will be permitted, but no electronic devices will be allowed.

A Solution example is available for the quiz.

Assignment A is posted.

Department of Mathematics, PO Box 643113, Neill Hall 103, Washington State University, Pullman WA 99164-3113, 509-335-3926, Contact Us