initialize normal random number generator

initrandn() sets the state for Matlab's normal (Gaussian) random number generator. (Matlab has two generators-- 'rand' and 'randn'-- for uniform and normal random numbers, respectively. Each of these maintains its own state).

If the optional calling argument is missing, initrandn() prompts the user to enter a seed interactively. If the optional calling argument is present but is an empty matrix, or if the user input is empty, a default seed is generated based on the current date and time.