Trying to make a reward with probability

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1

I am trying to give the player a reward with probability but it does not work as expected

It is based on a probability of 0 to 1, the problem is that it only returns 2 probabilities (the one of 0.800 and 0.500) and the rest never returns

This is the code:

local Rewards = {    
    {"Coins", 50, 0.800};
    {"Coins", 150, 0.500};
    {"Coins", 500, 0.310};
    {"Gems", 200, 0.100};
    {"Gems", 500, 0.035};
};

script.Parent.MouseButton1Click:Connect(function()
    local randomChance = math.random();
    local cumulativeChance = 0;
    
    for i, v in pairs(Rewards) do
        local Currency = v[1];
        local Reward = v[2];
        local Chance = v[3];
        
       cumulativeChance = cumulativeChance + Chance;
        
        if randomChance <= cumulativeChance and #v > 0 then
            print("You win", Reward, Currency, "The chance was", Chance)
            break
        end
    end
end)

I really appreciate if you could help me fix this problem, thanks for reading! :slight_smile:

1 Like
2

Its probably because you used “break”, remove it and it will probs work.

3

It can’t be that, the break makes me choose the reward

4

You could do this instead of a for loop:

local randomReward = Rewards[randomChance]
local currency = randomReward[1]
local reward = randomReward[2]
local chance = randomReward[3]

and try doing this in the randomChance

local randomChance = math.random(#Rewards)
5

I could do that but it’s not exactly what I want, I want this to have a “%” chance that it will give you that reward, if I do what you told me it would be much easier to get the hardest reward to get

6

The first one is 0%-80%, and the next is 80%-130%. You’re not going to ever get higher than 100%, so any other numbers won’t matter once you get to the one going up till 100%.

2 Likes
7

Here is my way of selecting things by chance:

local random = math.random(1,100)

if (random <= 30) then -- 30% chance

elseif (random > 30) then -- 70% chance

end
8

You don’t need the elseif, just else, and this is exactly what the person is doing already. They just did it wrong by creating probabilities over 1 (100%) so nothing else would ever be picked.

1 Like
9

math.random() with no arguments returns a number between 0 and 1 (I think).

I think its also possible to do:

local rand = Random.new(tick())
local sumOfAllChances
rand:NextNumber(0,sumOfAllChances)
10

You need to make so all the chances adding up equal to 1.

To convert your current chances to that (though it may not be accurate so I recommend doing it manually).

Take the sum of all the chances:
0.8+0.5+0.31+0.1+0.035

=

1.745

Divide every chance with 1.745 and set it as the new chance.

0.8/1.745

Do it with all the chances and it should work as expected, but still I recommend deciding all the chances again and make sure they add up to 1.

1 Like
11

yes i know that’s the reason why it doesn’t work but i can’t think of what to do to make it throw all the odds

12

Just have them add up to 100%. If you really can’t, multiply your random number by whatever they add up to (e.g. 1.745 here).

3 Likes
13

You can try something like this:

local sum = 0
for _, item in ipairs(choices) do
    sum += item.Weight
end

local rand = math.random(sum)
for _, item in ipairs(choices) do
    if rand < item.Weight then
        return item.Object
    end

    rand -= item.Weight
end

Example of “choices”:

local choices = {
    {Weight = 50, Object = "ok"},
    {Weight = 25, Object = "ok1"},
    {Weight = 25, Object = "ok2"},
}

algorithm is from here: c++ - Weighted random numbers - Stack Overflow

I’d recommend calculating the sum of the weights a single time instead every single time you need to pick, given that the choices are going to be the same each time. Make sure you pick a new random number each time though.

This doesn’t use percentages so the weights don’t have to add up to a hundred each time. If they do, you can just set the sum of the weights to 100 instead of counting them each time.

2 Likes
14

It worked :smiley: , I did not want to break my head adding each Chance so that in the end it reaches 100% since I want to add +10 Rewards so thanks to the help of @strategic and @rog I managed it, thanks for helping!

btw, the algorithm also served :slight_smile: