a short code for creating a random (1,-1) matrix

This is a very short code file for creating a random matrix whose entries are either 1 or -1.

Description

I have no idea whether this is the first one, but I am pretty sure that you guys can fully understand what can be done by this short and concise matlab code, that is, to generate a random matrix of any given order, with entries randomly chosen from {1,-1}. In fact, the code can be extended to produce any random matrix whose elements are randomly chosen from any dyadic set ,say, {a,b}. The work was originated and inspired by the blog of Terence Tao on random matrix (see the webpage:
http://terrytao.wordpress.com/tag/random-matrices/)
and a talk "Discrete random matrices " by P.M.Wood from Stanford on the BADMath day of Spring 2010, San Jose,CA.
The running of the code is very fast, as you can find. But it will sharply slow down and display "inf" on your command window if you
put "det" function involved to test its singularity. Sure we may avoid this by using instead a logic function.

• MATLAB release: MATLAB 7.7 (R2008b)

[James Tursa]

This submission has the following problems:
1) It uses a double for loop to individually fill in each element of the resulting matrix rather than using vectorized code.
2) It uses the relatively expensive power operator to generate the +1 and -1 values.
3) The H1 line function name does not match the actual function name.
4) A much faster (more than 3x faster) one-liner equivalent to this submission is as follows: floor(rand(n)*2)*2-1
5) There is no provision for non-square or multi-dimensional sizes. Only square 2D sizes are supported.

James Tursa

[Jos (10584)]

Indeed poorly coded using an unnecessary double-for loop (with pre-allocation though!), limited to 2D sqaure matrices only.

A vectorized, (too!) simple and flexible approach:

function R = rand01(varargin)
% H1 line goes here
% help goes here
R = 2*(rand(varargin{:})>0.5)-1 ;