function [ c, seed ] = i4_uniform_ab ( a, b, seed ) %*****************************************************************************80 % %% I4_UNIFORM_AB returns a scaled pseudorandom I4. % % Discussion: % % The pseudorandom number will be scaled to be uniformly distributed % between A and B. % % Licensing: % % This code is distributed under the GNU LGPL license. % % Modified: % % 12 November 2006 % % Author: % % John Burkardt % % Reference: % % Paul Bratley, Bennett Fox, Linus Schrage, % A Guide to Simulation, % Second Edition, % Springer, 1987, % ISBN: 0387964673, % LC: QA76.9.C65.B73. % % Bennett Fox, % Algorithm 647: % Implementation and Relative Efficiency of Quasirandom % Sequence Generators, % ACM Transactions on Mathematical Software, % Volume 12, Number 4, December 1986, pages 362-376. % % Pierre L'Ecuyer, % Random Number Generation, % in Handbook of Simulation, % edited by Jerry Banks, % Wiley, 1998, % ISBN: 0471134031, % LC: T57.62.H37. % % Peter Lewis, Allen Goodman, James Miller, % A Pseudo-Random Number Generator for the System/360, % IBM Systems Journal, % Volume 8, Number 2, 1969, pages 136-143. % % Parameters: % % Input, integer A, B, the minimum and maximum acceptable values. % % Input, integer SEED, a seed for the random number generator. % % Output, integer C, the randomly chosen integer. % % Output, integer SEED, the updated seed. % i4_huge = 2147483647; if ( seed == 0 ) fprintf ( 1, '\n' ); fprintf ( 1, 'I4_UNIFORM_AB - Fatal error!\n' ); fprintf ( 1, ' Input SEED = 0!\n' ); error ( 'I4_UNIFORM_AB - Fatal error!' ); end seed = floor ( seed ); a = round ( a ); b = round ( b ); seed = mod ( seed, i4_huge ); if ( seed < 0 ) seed = seed + i4_huge; end k = floor ( seed / 127773 ); seed = 16807 * ( seed - k * 127773 ) - k * 2836; if ( seed < 0 ) seed = seed + i4_huge; end r = seed * 4.656612875E-10; % % Scale R to lie between A-0.5 and B+0.5. % r = ( 1.0 - r ) * ( min ( a, b ) - 0.5 ) ... + r * ( max ( a, b ) + 0.5 ); % % Use rounding to convert R to an integer between A and B. % value = round ( r ); value = max ( value, min ( a, b ) ); value = min ( value, max ( a, b ) ); c = value; return end