I wrote the code found in this post in the Student Version of MATLAB R2009a (7.8.0.347) on Windows Vista SP2.
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function U = js_randv(i, x) %js_randv Pseudo Random Number Vector Generator % Returns a pseudo random number vector % according to congruential random number generator % i = length of vector % x = seed value of sequence % U = vector of Xi+1 = (a * Xi) mod m isFirst = 0; a = 16807; % 7^5 predetermined multiplicative value m = 2147483647; % 2^31-1 predetermined prime number r = 2836; % m div a q = 127773; % m mod a T = zeros(1, i); % holds seed values U = zeros(1, i); % holds returned uniform random numbers in (0,1) % loop through all indices of vector for j=1:i % if this is the first value, use seed if isFirst == 0 seed = (a * mod(x, q)) - (r * (x / q)); T(1, j) = seed; isFirst = 1; % if this is not the first value, use current index else previousValue = T(1, j-1); seed = (a * mod(previousValue, q)) - (r * (previousValue / q)); T(1, j) = seed; end U(1, j) = seed / m; end end |
This function will return a vector of size i containing randomly generated numbers uniformly distributed between 0 and 1. It’s not perfect, but it got the job done. I’ll get around to explaining it more beyond the meager comments another time.
References:
Generating Random Numbers
Linear congruential generator
Hi!
My name is Anna and I want to thank you for posting this code, I need to modify the code for a project digital image processing, where I need a pseudo random noise sequence and researching I came to this was reduced to generate a sequence of random numbers . The particularity of the noise I create is that I should only have values between -1, 0 and 1 and then there’s my mission. Thank you very much again!
Sorry for my bad English 😛
Hi Anna. What type of distribution are you trying to generate these numbers under? Uniform, random, etc. See: http://www.mathworks.com/access/helpdesk/help/techdoc/ref/rand.html for an easy way to generate matrices of uniformly distributed numbers and http://www.mathworks.com/access/helpdesk/help/techdoc/ref/randn.html for normally distributed numbers.
My method of generating random numbers is a bit cumbersome, but seemed to work for my application. It may not work for yours. Good luck!
My method of generating random numbers is a bit cumbersome, but seemed to work for my application. It may not work for yours ?
Free ?