1. Programming The ideal style of programming is Structured or
Modular programming
Break down a larger goal into tasks
Develop a module for each task
A module has a single entrance and exit
Modules are reusable

2. A structured program for building a house:
Excavation
Foundation
Framing subroutine - floor 1
Framing subroutine - floor 2
Walls
Bathroom subroutine
etc.
Excavation routine
Foundation routine
Framing routine

3. Framing routine
measure wood
cut wood
assemble pieces
put frame in place
attach frame
Each of
these can
have
subroutines

4. Comments!!! Another aspect of good programming:
You must include comments in your programs you turn in - otherwise we will have great difficulty knowing what you are doing

5. For example, here some cryptic code without comment
for j=0 to 2
k=(2-j)*(1+3*j)/2
end
What does it do?
Put a comment in
/* turns (0,1,2) into (1,2,0) */

6. Matlab is a numerical analysis system
Can write “programs”, but they aren’t compiled
Should still use structured programming
Should still use comments
Comments are indicated by % at the beginning of the line

7. Matlab’s basic component is a vector
All operations are optimized for vector use
Loops run slower in Matlab than in Fortran (not a vector operation)
Really good help command

8. Matlab topics and how it differs from Fortran
Syntax
Data types
Input-output
Mathematics
Do loops
If then structures

9. Syntax
No complicated rules
Perhaps the most important thing to remember is semicolons at the end of a line surpress output
Type more on to keep text from leaving screen too fast

10. Data types
All numbers are double precision
Text is stored as arrays of characters.
You don’t have to declare the type of data (defined when running)

11. Vectors
Everything in Matlab is a vector (or matrix)
Even single value variables
size command gives size of a vector

12. Example Pi= a= » pi » a=[1 2; 3 4] ans = 3.1416 a = 1 2 » size(pi) 3 4
» a=[1 2; 3 4]
a =
» size(a)
ans =
Pi= a=

13. Input-output
Values can be assigned by typing vector name = value
Matlab automatically prints the results of any calculation (unless surpressed by ;)
Use disp to print out text to screen

14. To read files in
- if the file is an ascii table, use load
- if the file is ascii but not a table, file i/o needs fopen and fclose
Reading in data from file using fopen depends on type of data (binary or text).

15. Mathematics
All the standard operators +,-,*,/,^
Built-in functions too
sin(), cos(), exp(), etc.
IMPORTANT
These operators are vectorized.

16. Example: Vectorized operators
But a*b gives an error because dimensions are incorrect. Need to use .*

17. Likewise

18. for loops
They do exist in Matlab, and sometimes you need them
for i=1:n
for j=1:n
a(i,j)=1/(i+j-1);
end

19. Because of vectorization , can often do loops more efficiently
for i=1:3
b=sin(i)
end
i=1:3
b=sin(i)
is much faster

20. If - then also exists
The general form of the IF statement is
IF expression
statements
ELSEIF expression
ELSE
END

21. Possible comparisons are
= = equals
< less than
> greater than
<= less than or equal to
>= greater than or equal to
~= not equal to

22. Programming
In Matlab, one can write a set of commands in a text file (called an m-file, since the ending must be .m)
These commands can be a program
Type the name of the m-file in the Matlab environment to run the program

23. Difference betweem scripts and functions
Scripts share variables with the main workspace
Functions do not

24. One of the best things about Matlab is graphics
plot is the one you will be using most often
many other 3 dimensional plotting functions