MATLAB: An introduction

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MATLAB An introduction

• Christian Ruff

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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

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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

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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/suppo
  rt/ 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/matl
  abcentral/

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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

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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

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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

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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