Matlab

1
Matlab refresher
Your objective to dominate! My objective to
help you dominate!
2
Some references

• MATLAB Student Version Learning MATLAB, The
  MathWorks, Inc.
• Introduction to MATLAB 6 for Engineers, W.J.Palm
  III, McGraw-Hill.
• Numerical Methods with MATLAB, G.Recktenwald,
  Prentice Hall.

3
Key concept the Workspace (WS)

• The Workspace (WS) contains all of your currently
  active variables and relations.
• These are initially entered by typing commands
  (most likely).
• Useful Workspace commands
• Clear empty the WS
• Who (whos) show what is in the WS
• Save ltfilenamegt save all WS variables to file
• Load ltfilenamegt retrieve a particular WS from
  file

4
Key concept WS inputs
Command line inputs
WORKSPACE
Script file inputs
Workspace file inputs
5
Key concept WS outputs
Diary files
WORKSPACE
Workspace files
Graphics (plot) files
6
Script files

• Script files are text files that are created
  using the MATLAB script file editor. They usually
  have the suffix .m.
• A script file can be run from the command line or
  toolbar.
• Two items to remember about .m files
• Use to enter comments for your use.
• Use at the end of lines to suppress echo
  printing when the file is run.

7
More about the Workspace

• Recording your MATLAB session can be useful for
  documentation.
• Useful Workspace commands
• Diary ltfilenamegt turn on recording of all text
  i/o except plots, save into ltfilenamegt
• Diary off turn off current recording
• Path pointer to current directory
• Pathtool directory browser

8
A typical session pattern

• Clear
• Diary Problem1
• create data etc here
• Pa 14.7 R 245.6 P 23 Q (1/R)(P-Pa)
• who
• Save Problem1Run1
• Diary off

• You now have 2 files
• Problem1 a diary of this session
• Problem1Run1 a WS file that can be used to
  recover your last state by using a Load command

9
Solving Linear Algebraic Equations

• Define a set of linear algebraic equations as
  follows
• AX BU
• X is the unknown vector (n x 1)
• U is the input vector (m x 1)
• A is n x n, B is n x m
• In the WS define A, B, and U.
• Then type X inv(A)BU

Click here to see an example session LAExample1
10
Solving Linear Algebraic Equations

• Dominators know that a unique solution to a
  problem in linear algebra doesnt always exist.
  To investigate before you leap try this
• Use the command det(A) to check the determinant
  of A. Proceed accordingly.
• Sometimes we seek insight in the form of
  eigenvalues of A. Try this
• Type Evals eig(A).

Click here to see an example session LAExample2
11
Solving Linear Differential State Equations

• Define a set of linear algebraic equations Xdot
  AX BU
• Xdot is the first derivative of X.
• Create a script (.m) file that defines the
  equations for MATLAB in a specific format.
• for example LDEEqns1.m
• Create a script file that controls the solving of
  the problem.
• click to see an example LDEExample.pdf