matlab tips and tricks and ...

page overview:

I created this page as a vectorization helper but it grew to become my annotated Matlab reading cache. In order to motivate the DSP people out there, I am showing below how one can apply a window and scale factors on a pre-framed signal using no loops and minimal memory.

% For framing use buffer() or your own favorite
% Frame length: 256, Number of frames: 10000
X = randn(256,10000);

% Make a window (same for each frame)
w = hamming(256);
W = diag(sparse(w));

% This is the windowed signal, without loops
XW = W * X;

% Make a vector of random gain factors (one per frame)
g  = rand(10000,1);
G  = diag(sparse(g))

% Now lets scale each frame by the corresponding gain factor
XG = X * G;

% Windowing and gain scaling is just left and right product with a diagonal.
XWG = W * X * G;

local links:

Note that some of the following documents are taken off of Mathworks' own support site; more specifically take a look at the technical notes section.  Also a very good source of information is comp.soft-sys.matlab
 

• MATLAB Tensor Toolbox, 2005-12-07
  Just as I was about to bite the bullet and write it myself, I finally came across a class for multidimensional tensors. The original page describing the toolbox can be found here and the code here.  If you are working with multi-linear forms you will definitely appreciate this.
   
• GUI with MATLAB, 2005-06-15
  A presentation on how to get started with GUIs.
   
• Good MATLAB Programming Practices for the Non-Programmer, 2005-06-15
  Some simple suggestions.
   
• Writing Fast MATLAB Code, 2005-04-23
  Once again your regular collection of standard tricks.
   
• MATLAB Programming Style Guidelines, 2005-04-23
  Not that you will ever start writing with such style but here is a bunch of suggestions.  Well on page 9 it reads "Avoid cryptic code",  well I don't think so.  Can you deny that x'.' is so much more beautiful than conj(x) ???  I always prefer the second cause it's so easy to type ... ;)
   
• MATLAB Tips and Tricks, 2005-04-23
  We share the same name.  A collection of a lot rather straightforward code.  Take a look, you might find what you are looking for or might not ...
   
• Why does LPC return a different prediction error than ARYULE?, 2004-03-16
  This Matlab bug has caused me hours of frustration. Petr Fousek suffered too ...
   
• MEX-files Guide, 2004-03-04
  I still don't know if it is possible to operate 'inplace' on a mex array. Do I really need to reallocate memory for output?
   
• Why do I receive a segmentation violation mentioning the toolbox cache when starting MATLAB?, 2004-03-03
  Well you got to love this line: "Some customers have found that updating the driver for your video card can resolve the problem as well." Remember that we are talking about an XML toolbox cache file corruption ...
   
• Numerical Computing with MATLAB, (pdf cached), (code cached), 2004-02-20
  A very good read. Most of the chapters of the book along with the code are available online.
   
• MATLAB Array Manipulation Tips and Tricks (pdf cached), (code cached), 2003-06-14
  Again a very good read.
   
• Floating Point, IEEE Standard unifies arithmetic model (pdf), 2003-06-14
   
• Why do I receive errors when overloading SUBSREF for types {} and . for MATLAB OOPS objects (31436) (pdf), 2003-06-11
  If you have ever tried to write your own classes in Matlab chances are you run into the problems described in this article.
   
• Simplify your code with comma-separated lists (pdf), 2003-06-08
  Two very valuable cases are presented. The first is the fftshift() function which is all you need to know about the most flexible indexing method in Matlab. When you really understand fftshift() take a look at flipdim() and you are done. The second is the problems with subsref() / subsasgn() and the overloaded numel() functions in user-designed classes.
   
• What's the big deal ? (pdf), 2003-06-08
  The two main uses of deal are explained:
  [C{:}]   = deal(S.name); % The only way to initialize cell arrays
  [S.name] = deal(C{:});
   
• Exploiting the comma-separated list (pdf), 2003-06-08
  There is no exploiting going on here. This is a very easy reading.
   
• Think Globally, Act Locally (pdf), 2003-06-08
  A nice pattern for variable number number of input arguments is mentioned.
  function heatmodel(varargin)
  defaultValues              = {100,72,350};
  nonemptyIdx                = ~cellfun(‘isempty’,varargin);
  defaultValues(nonemptyIdx) = varargin(nonemptyIdx);
  [sz normalTemp hotTemp]    = deal(defaultValues{:});
   
• Picking up the Pace with the MATLAB profiler (pdf), 2003-06-08
  Some pretty interesting optimization tricks like the use of 1i variable, loop variable confinement and unrolling of complex arithmetic. Had MathWorks done this for all those cryptic "x" messages in profiler life would be easier ...
   
• Is it possible to run MATLAB in the background under UNIX ? (86) (pdf), 2003-06-04
  Guess what? It is!
   
• Techniques for Debugging MATLAB M-files (1207) (pdf), m-files (zip), 2003-05-13
  If you are a newbie and you're having problems with basic errors download the above m-files. Chances are your error is identified and solved in one of the examples.
   
• What Is the EVAL Function, When Should I Use It, and How Can I Avoid It ? (1103) (pdf) 2003-03-19
  Info about the dreaded triple quotes ''' in eval(). A really nasty way to disable quote's special functionality. In other languages one would expect to escape the quote by \' but not in Matlab. What you really need to know is that:
  >> eval('disp(''''''This is a string'''''')')
  'This is a string'
   
• Is it possible to call a dynamic linked library from MATLAB ? (33513) (pdf), m-files (exe) 2003-03-09
  Now one can simply wrap her code in a DLL and have it called from Matlab. Pointers to any type of Matlab variables can be defined straight in the workspace and can be passed to C/C++. Call by reference is now possible.
   
• Printing and Exporting Guide (1206) (pdf) 2003-02-27
   
• Exporting Figures for Publication B (pdf), m-files (zip) 2003-02-27
  Use this library in your next LaTeX paper ...
   
• Matrix Indexing in Matlab (pdf)
   
• Memory management guide (1106) (pdf)
   
• Accelerating Matlab (R13) (pdf)
  The new version of Matlab uses Just-In-Time code generation. Your for loops have never been that fast !
   
• Fast manipulation of multi-dimensional arrays in Matlab (pdf)
  (Older version here)
   
• How do I vectorize my code ? (1109) (pdf)
   
• Matlab array manipulation tips and tricks (pdf)
  See up for the newest version of this document.
   
• Matlab Tricks (pdf)
   
• comp.soft-sys.matlab.faq (pdf)
   
• Vectorization (pdf)

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