1. Matlab Workshop
9/22/2018

2. Useful links The help links on this page include
The help links on this page include
Mathworks’ Getting Started (the official online documentation of Matlab)
Kermit Sigmon’s MATLAB Primer (a very good beginner manual);
University of Utah’s MATLAB Tutorial and some others.
MATLAB’s online help manual

3. What is MATLAB?
MATLAB is a matrix-based tool for numerical computations. It’s very powerful and easy to use.
Both programming language and interactive environment
Very fast native functions; very slow when processing loops
Lots of available toolboxes

4. Acquiring Matlab
Free for Yale students

5. Launching Matlab Click “MATLAB 7” from the start menu
(on Unix systems: type “matlab” to enter interactive mode)

6. The Interface Main Window: Input/Output
Workspace: consists of the variables you create during a MATLAB session;
Command History: double click them to evaluate them;
Current Directory browser: shows you where you are.

7. Tips Can use Matlab as a calculator
Type “help” for a list of all help topics
help abs gives the syntax and information about the absolute value command

8. Entering Matrices Matrices can be
Entered manually A = [1 2 3 ; ; 7 8 9]
Generated by built-in functions
Loaded from a file

9. Matrix operations: + addition - subtraction * multiplication ^ power
‘ transpose
\ left division, / division
x = A \ b is the solution of A * x = b
x = b / A is the solution of x * A = b
To make ‘*’ , ‘^’, ‘\’ and ‘/’ apply element-by-element, we precede the operators by ‘.’

10. Subscripts:
Subscripts: the element in row i and column j of A is denoted by A(i, j).
i,j can also be vectors of indices or logical arrays: A=4*[ ]’ b=A>18; c=[ ]’
A(b), A(c)

11. The Colon Operator ‘:’
The colon ‘:’ is one of MATLAB ’s most important operators. It has many formats:
Subscript expressions involving colons refer to portions of a matrix:
A(5:9) is the fifth to the ninth elements of A.
[0:0.2:3] is a row vector containing integers from 0 to 3, in increments of 0.2

12. Matrices and Random Numbers:
Four functions that generate basic matrices:
Zeros: all zeros. A = zeros(1,3)
Ones: all ones. A = ones(2,4)
Rand: elements are U[0,1] random variables A = rand(3,5)
Randn: elements are standard-normal random variables A = randn(2,5)
Be careful: Matlab always sets the same seed. Get ‘more random’ numbers by typing rand('state', sum(100*clock))

13. A=eye(3) gives a 3-by-3 identity matrix
sparse(m,n): same as zeros(m,n), use if most elements are zeros.
Concatenation: join small (compatible) matrices to make bigger ones:
B = [A A-2; A*2 A/4]
Deleting rows and columns:
B(:,2) = [ ]

14. Suppressing Output: C = randn(5,1);
If you simply type a statement and press Enter, MATLAB automatically displays the results on screen. If you end the line with a semicolon ‘;’, MATLAB performs the computation but does not display any result.
Example: C = randn(5,1) v.s.
C = randn(5,1);

15. Functions:
MATLAB provides a large number of standard elementary mathematical functions, including abs, sqrt, exp, sin.
For a list of the elementary mathematical functions, type:
help elfun
For a list of more advanced mathematical and matrix functions, type
help specfun
help elmat

16. Programming with MATLAB:
Files that contain code in the MATLAB language are called M-files. You can create M-files using the matlab editor, then use them as you would any other MATLAB functions or commands. There are two types of M-files: Scripts and Functions.

17. Scripts
Scripts: a bunch of code grouped together; doesn’t accept argument or return output.
Example
open m-file editor
type disp(‘Hello’)
save as test.m in your current directory

18. Functions:
Functions are M-files that can accept input arguments and return output arguments. The name of the M-file and of the function should be the same.
For example, save this as area.m: function ar = area(radius) ar=pi*radius^2;

19. Flow Control: MATLAB has following flow controls: If statement
For loops
While loops
Continue statement
Break statement

20. if … elseif … else … end if A > B 'greater' elseif A < B 'less'
'equal'
end

21. for … end beta=0.925; a=1:1000; for i = 1:1000 betavec(i)=beta^a(i)
But you should avoid for loops if possible
newbetavec(a)=beta.^a

22. Graphics: plot x = [0 : .01 : 2*pi]; y = sin(x); plot(x,y)
plot(x,y,x,y2,x,y3)

23. Learn from others
There are lots of Matlab functions already out there:
Search the internet for them!
James LeSage’s econometrics toolbox: