The RANDOMN function returns one or more normally-distributed, floating-point, pseudo-random numbers with a mean of zero and a standard deviation of one.
RANDOMN uses the Box-Muller method for generating normally-distributed (Gaussian) random numbers.
A long integer used to initialize the IDL random number generator. Both of the random number generators, RANDOMN and RANDOMU, simulate random floating point numbers using a seqence of long integers. You can use Seed to start the sequence. IDL saves the sequence for subsequent calls to RANDOMN and RANDOMU. If Seed is a named variable, RANDOMN and RANDOMU will update it to the next long integer in the sequence.
NOTE: RANDOMN and RANDOMU use the same sequence, so starting or restarting the sequence for one starts or restarts the sequence for the other. Some IDL routines use the random number generator, so using them will initialize the seed sequence. An example of such a routine is CLUST_WTS .
The formulas for the binomial, gamma, and Poisson distributions are from section 7.3 of Numerical Recipes in C: The Art of Scientific Computing (Second Edition), published by Cambridge University Press.
Set this keyword to a 2-element array, [ n , p ], to generate random deviates from a binomial distribution. If an event occurs with probability p , with n trials, then the number of times it occurs has a binomial distribution.
Set this keyword to an integer order i > 0 to generate random deviates from a gamma distribution. The gamma distribution is the waiting time to the i th event in a Poisson random process of unit mean. A gamma distribution of order equal to 1 is the same as the exponential distribution.