Question

I’d like something (a “target”) to show up five times in a random order (out of a total of 10 times).

The problem with the code below is I can get it to show up in a random order, but not necessarily five times:

function rand_float(min:Number,max:Number=NaN):Number {
            if (isNaN(max)) { max = min; min=0; }
            return Math.random()*(max-min)+min;
}

function rand_integer(min:Number,max:Number=NaN):int {
        if (isNaN(max)) { max = min; min=0; }
        return Math.floor(rand_float(min,max));
}
function rand_boolean(chance:Number=0.5):Boolean {
    return (Math.random() < chance);
}

var a_list:Array = ['a','b','d','e'];

var target:String = 'b';

for (var i:int = 0; i < 10; i++) {
    if (rand_boolean()) {
        trace('random other thing: ' + a_list[rand_integer(0,3)]);
    } else {
        trace('target! :' + target);
    }
}

Because the rand_boolean method is 50-50, it either “shows up” or “does not show” but there’s no guarantee it will always be 5 times out of 10.

I guess I could put in a counter and then limit it after 5 times (if it goes over) or force it to show up more (if say, after 8 times it has only shown up once) but is there perhaps a better way to go about doing this?

Answer 1

One simple solution: create a list of possibilities with the correct amount of the desired target.

['a','a','b','b','b','b','b','c','c','d']

Create a copy of it, remove each item as you pick them. Once you’ve pulled all 10, re-copy the list.

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Alternatively, you can create this list by seeding it with 5 ‘b’s, selecting at random 5 ‘a’,’c’, or ‘d’, and then you have your list to select from randomly, if you don’t want the non-‘b’ counts to be consistent.

To generate the random item array:

var targets:Array = ['b','b','b','b','b'];
var options:Array = ['a','d','e'];

var current:Array = new Array(targets);

while (current.length < 10)
{
    current.push(options[rand_integer(0,3)]);
}

And then in your random selection:

var item:String;
if (current.length == 0)
    //regenerate array using above code

//splice(index to start at, # of items to remove) returns an array, we grab the first (only) item in it
item = current.splice(rand_integer(0,current.length),1)[0];