Transcript Cross-modal’ reward signals in primary visual and

MATLAB: An introduction
Christian Ruff
Course overview
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Autumn 2007: Using MATLAB for data analysis and visualisation
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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
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Spring 2008: Using MATLAB to run experiments and collect data
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April or May 2008: SPM – a MATLAB “toolbox”
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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
What is MATLAB?
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“MATrix LABoratory”, a high-level programming language / computing environment
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Developed in the late 70s for computer science students
 commands for linear algebra routines (matrix operations)
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Now also contains ‘intuitive’ routines for graphing, user interfaces, hardware control
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Today most popular environment in scientific computing (ahead of Mathematica,
Octave, or Python); over 1.000.000 users in science, engineering, industry, etc.
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Learning MATLAB is good for almost any scientist
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Many specialised toolboxes available (e.g., statistics; neural network modelling; image
processing, etc.)
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A lot of code for specific scientific purposes freely available on the internet (e.g., COGENT,
PSYCHTOOLBOX, SPM, ANSLAB)
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Easy to modify existing routines / write your own code / learn how others solve problems
How do I get started?
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http://www.mathworks.com
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Academic license is £128 for basic package; £128 for each toolbox (e.g.,
statistics); free trial version available
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Windows, Mac, LINUX versions
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Excellent documentation and tutorial (both online and in pdf form) at
http://www.mathworks.com/support/ or by typing help or doc in MATLAB
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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/
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A good book: “Mastering Matlab” by Hanselmann and Littlefield
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Lots of functions at http://www.mathworks.com/matlabcentral/
Demo: Structure and handling of MATLAB
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Starting MATLAB
Command window
Evaluating commands: comma and semicolon
Variables: Scalars and matrices
operators
errors
Help (F1) / doc
cls
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Workspace
Clear: variables and all
load / save .mat files
Current directory, pwd, ls, cd + graphical options for this
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Command history; arrow up/down
Editor: save series of commands as .m files, execute with F9 / button / run
Dock editor
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
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:
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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
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