Sol's RNG type function with a plus

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#1

Hello,
I’m looking for a function that can sort through a table of possibilities each with their own unique chance of occurring and pick one, but I also want it to account for multiples wherein the total chance is the product of all possibilities chosen.

local Items = {
	{"Bronze", 0.5},
	{"Silver", 0.25},
	{"Gold", 0.1},
	{"Diamond", 0.01}
}

print(GetRandom(Items))

--> Output:
--[[
Bronze - 0.5
Bronze - 0.5
Silver - 0.5
Bronze - 0.5
Bronze & Silver - 0.5 * 0.25 = 0.125
Gold - 0.1
Silver - 0.25
Bronze - 0.5
]]

Although Bronze & Silver was never written in the table of possibilities it can still occur with a rarity of 0.125 or in other words a 1 in 8 chance. The same logic applies to possibilities such as Bronze, Silver & Diamond and all number of possibilities. In this case with a table of 4 possibilities there should be a total of 2^4 (16) possibilities including combinations.

I appreciate anyone who helps.

#2

As a starting point you could edit this script, perhaps it will give you some ideas on how to achieve your system.

-- Function to calculate factorial
local function factorial(n)
	if n == 0 then
		return 1
	else
		return n * factorial(n - 1)
	end
end

-- Function to generate combinations of items and their probabilities
local function generateCombinations(items)
	local combinations = {}
	local n = #items  -- Number of items in the table

	-- Loop through all possible combinations using binary representation
	for i = 0, 2^n - 1 do
		local combination = {}
		local probability = 1.0

		-- Check each bit of the binary representation
		for j = 1, n do
			if bit32.band(i, 2^(j-1)) ~= 0 then
				table.insert(combination, items[j][1])
				probability = probability * items[j][2]
			end
		end

		-- Store the combination and its probability in the result table
		if #combination > 0 then
			table.insert(combinations, {table.concat(combination, ", "), probability})
		end
	end

	return combinations
end

-- Main function to get a random item or combination from the table
function GetRandom(items)
	-- Generate all possible combinations with their probabilities
	local combinations = generateCombinations(items)

	-- Select a random combination based on the calculated probabilities
	local totalProbability = 0
	for _, combo in ipairs(combinations) do
		totalProbability = totalProbability + combo[2]
	end

	local randomValue = math.random() * totalProbability
	local accumulatedProbability = 0

	for _, combo in ipairs(combinations) do
		accumulatedProbability = accumulatedProbability + combo[2]
		if randomValue <= accumulatedProbability then
			return combo[1] .. " - " .. string.format("%.4f", combo[2])
		end
	end

	return "No item selected"  -- This should never happen
end

-- Example usage
local Items = {
	{"Bronze", 0.5},
	{"Silver", 0.25},
	{"Gold", 0.1},
	{"Diamond", 0.01}
}

-- Test the GetRandom function
for i = 1, 8 do  -- Adjust the number of trials as needed
	warn(GetRandom(Items))
end

OUTPUT:
snap