% TRIRND2   Generate numbers from a 0-centered triangular distribution
%
% Density is f(x) = 1-abs(x) for x in [-1,1].
%
function X=trirnd2(m,n)
if nargin<1, m=1; end
if nargin<2, n=m; m=1; end

% Simple method: Take [0,1]-distributed triangular randoms
% like in TRIRND.  Then randomly (0.5 chance) either shift left
% by 1 unit into the interval [-1, 0], or mirror left-right
% inside the [0,1] interval
% (There are other methods but this is easy.)

U = unifrnd(0,1,m,n);
X = sqrt(U);

% Choices for shifting (V=1) or mirroring (V=2)
V = randi(2,m,n);
X(V==1) = X(V==1) - 1;
X(V==2) = 1 - X(V==2);