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MATLAB for Research and Classwork: An Easy-to-Use Tool

Explore the basics of MATLAB, loading/saving data, matrices, graphing, and visualization. Utilize high-level programming for rapid prototyping and publication-ready figures. Interact efficiently via command line or GUI.

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MATLAB for Research and Classwork: An Easy-to-Use Tool

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  1. MATLAB For research, classwork, and publications Holly Dail

  2. Introduction • Easy to use tool for: • numeric computation • advanced graphics & visualization • high-level programming language • On csehelp administered suns: • /opt/matlab/bin/matlab • Student version ~$100 at bookstore • 1 package -- both windows and linux Holly Dail

  3. Outline • Basics of MATLAB • Loading data and saving results • Matrices and computation • Graphing • Exporting your results • Final comments Holly Dail

  4. MATLAB Components • Variables: C-like, automatically-allocated, overloaded functions simplify handling • Language: high-level language, more intuitive than C constructs • Programming: • Interactive command line interface • Script a set of commands in a .m file • Encapsulate a function in a .m file • Graphics windows Holly Dail

  5. Getting around • Accessing help: • ‘help’, ‘helpwin’ (GUI), ‘lookfor’ (search) • Workspace information: • ‘whos’: list current variables • ‘what’: list MATLAB-specific files in cwd • ‘which’: locate files Holly Dail

  6. Getting around • Understanding functions: • ‘type functionName’: prints out the code for the function • Works w/ most MATLAB functions • Learn from available code (or remember your math) • OS commands: • ‘cd’, ‘copyfile’, ‘getenv’ • ‘!’ (execute OS command in shell) Holly Dail

  7. Interacting with MATLAB • The desktop • Easy to learn, comprehensive GUI environment • Slow rendering in Linux, Sun …. VERY slow over a network • Command line only • More difficult to learn • No waiting for rendering, less ‘mouse’ work Holly Dail

  8. Demo: basics Holly Dail

  9. Loading data • ‘load myData.txt’ • Use with plain text file with a full matrix • Comments begin with ‘%’ • Automatically stored in variable ‘myData’ • Text: ‘fopen’, ‘fgetl’, ‘fscanf’, ‘input’ (user input) • HDF: NCSA’s Hierarchical Data Format • Others: ‘imread’ (images), ‘wavread’ (audio), ‘aviread’ (movie) Holly Dail

  10. Saving results • Symmetric functions to reading • ‘save myWork.dat’ • Save your MATLAB workspace (half-finished work, new results) in a binary file • Restore work with ‘load myWork.dat’ Holly Dail

  11. Matrices • Syntax: • ‘[]’: Brackets define a matrix • ‘,’: commas separate columns (== space) • ‘;’: semicolons separate rows • X’: transpose of x • ‘:’: full range (i.e. all columns) • ‘1:5’: first 5 elements Holly Dail

  12. Example data set • Measured iteration times for 100 iterations of Jacobi • Mostly standard results, 1 extreme outlier • File contains • A comment at top (starts with ‘%’) • Column 1: iteration # • Column 2: iteration time (sec) Holly Dail

  13. Demo: matrics, loading, & saving Holly Dail

  14. Demo: graphing Holly Dail

  15. Exporting to tables • ‘save -ascii myFile.txt myMatrix’ • Saves as plain text -- load into word, excel directly • ‘writeTexTable(matrix, fileName, fmt)’ • Writes a TeX formatted table • Ready for use in a LaTeX: \input{…} • ‘fmt’ describes the row format • Not MATLAB standard … written by Otto Sievert Holly Dail

  16. Exporting to figures • ‘print -dpsc2 myFig.ps’ • Prints current figure window as level 2 postscript file • Ready for use in LaTeX: \epsfig{…} • Other possibilities: -dpng, -dtiff, -djpeg • See with ‘!gv myFig.ps’ • Output jpegs -> mpeg_encode -> portable movie Holly Dail

  17. Demo: exporting++ Holly Dail

  18. Final comments • Data analysis & visualization • Figures and tables for publication • Rapid prototyping • Learning about and experimenting with techniques you don’t know well Holly Dail

  19. Slides and demos online: • www.cs.ucsd.edu/groups/csegsa/enrichment.html • Questions & help: hdail@cs.ucsd.edu • Questions? Holly Dail

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