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MATLAB: An introduction

MATLAB: An introduction. Christian Ruff. Course overview. Autumn 2007: Using MATLAB for data analysis and visualisation Session 1: Introduction Session 2: Data types, handling data Session 3: Statistical data analysis and Visualisation Session 4: Producing graphs in MATLAB

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MATLAB: An introduction

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  1. MATLAB: An introduction Christian Ruff

  2. Course overview • Autumn 2007: Using MATLAB for data analysis and visualisation • Session 1: Introduction • Session 2: Data types, handling data • Session 3: Statistical data analysis and Visualisation • Session 4: Producing graphs in MATLAB • Session 5: User-defined Topics, questions and answers • Spring 2008: Using MATLAB to run experiments and collect data • April or May 2008: SPM – a MATLAB “toolbox” • Summer 2008: Advanced experimental and data analysis procedures  Practical demonstration with code, not lecture  All materials online at http://www.icn.ucl.ac.uk/courses/MATLAB-Tutorials/index.htm

  3. What is MATLAB? • “MATrix LABoratory”, a high-level programming language / computing environment • Developed in the late 70s for computer science students  commands for linear algebra routines (matrix operations) • Now also contains ‘intuitive’ routines for graphing, user interfaces, hardware control • Today most popular environment in scientific computing (ahead of Mathematica, Octave, or Python); over 1.000.000 users in science, engineering, industry, etc. • Learning MATLAB is good for almost any scientist • Many specialised toolboxes available (e.g., statistics; neural network modelling; image processing, etc.) • A lot of code for specific scientific purposes freely available on the internet (e.g., COGENT, PSYCHTOOLBOX, SPM, ANSLAB) • Easy to modify existing routines / write your own code / learn how others solve problems

  4. How do I get started? • http://www.mathworks.com • Academic license is £128 for basic package; £128 for each toolbox (e.g., statistics); free trial version available • Windows, Mac, LINUX versions • Excellent documentation and tutorial (both online and in pdf form) at http://www.mathworks.com/support/ or by typing help or doc in MATLAB • Other MATLAB tutorials on the web: • http://www.icn.ucl.ac.uk/webspace/users/ahamilton/matlab.htm • http://www.mrc-cbu.cam.ac.uk/Imaging/Common/matlab.shtml • http://www.indiana.edu/~statmath/math/matlab/ • A good book: “Mastering Matlab” by Hanselmann and Littlefield • Lots of functions at http://www.mathworks.com/matlabcentral/

  5. Demo: Structure and handling of MATLAB • Starting MATLAB • Command window • Evaluating commands: comma and semicolon • Variables: Scalars and matrices • operators • errors • Help (F1) / doc • cls • Workspace • Clear: variables and all • load / save .mat files • Current directory, pwd, ls, cd + graphical options for this • Command history; arrow up/down • Editor: save series of commands as .m files, execute with F9 / button / run • Dock editor

  6. Demo: Functions • Functions: function [output1,output2,…] = myfun(input1, input2,…) • Functions: • Input needs to be defined in command, output not • Function workspace: a separate module of the workspace • contains inputs to functions, transformation variables, and outputs from function • These variables are not visible from the global workspace • Functions can call other functions and contain subfunctions • Commands without semicolon are visible in command window • Graphical output is visible

  7. Demo: Functions in MATLAB • MATLAB – just a collection of functions: • Built-in functions cannot be edited but have an .m-file (for help) • Add-on functions are just an ordinary .m file that you can see/edit/add • How MATLAB finds a function: • Embedded in the function as subfunction • Built-in functions • Local directory • Path in descending order • Add functions to directory outside of the MATLAB toolbox (e.g., ‘work’ – otherwise MATLAB might overwrite them when re-installed • Dependency report

  8. Demo: Errors and debugging • Errors in functions: • Error message with pointer to problem (but workspace problem) • Help text and doc text • debugging mode: access the function workspace and go through code/functions step by step: • Stop if error • Breakpoints

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