I would like to return an array which has a set of unique elements randomly distributed according to custom frequency. My real world use-case is the repetition of carousel images based on a qualitative weighting of how popular those images are.
E.g. suppose I have 5 elements with weights:
A, 20% B, 50% C, 80% D, 10%
I would like to write a function that, given a length, tries to approximate a sequence such that C will appear eight times more often than D; D will appear 5 times less often than B; A will appear three times less often than C.
C will appear eight times more often than D; D will appear 5 times less often than B; A will appear three times less often than C.
You can do that with a weighted array of your elements:
var elems = ["A", "B", "C", "D"];
var weights = [2, 5, 8, 1]; // weight of each element above
var totalWeight = weights.reduce(add, 0); // get total weight (in this case, 16)
function add(a, b) { return a + b; } // helper function
var weighedElems = [];
var currentElem = 0;
while (currentElem < elems.length) {
for (i = 0; i < weights[currentElem]; i++)
weighedElems[weighedElems.length] = elems[currentElem];
currentElem++;
}
console.log(weighedElems);
This will produce an array like
["A", "A", "B", "B", "B", "B", "B", "C", "C", "C", "C", "C", "C", "C", "C", "D"]
so you can choose randomly from that like so
var rnd = Math.floor(Math.random() * totalWeight);
console.log(weighedElems[rnd]);
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