Creates a random vector which sums to 1. This is equivalent to creating a pie chart with a given number of slice: the size of each slice is random but the total is equal to 100%
The number of slices you want in your pie
The noise based random number generator used
The first index to use in the rng
https://stackoverflow.com/questions/53279807/how-to-get-random-number-list-with-fixed-sum-and-size
Creates a random vector which sums to 1. This is equivalent to creating a pie chart with a given number of slice: the size of each slice is random but the total is equal to 100%