[Feedback] Unstoppable mutator destroys Olexra and Blade Trap

Grim Dawn Ideas and Feedback
19
full mutator randomizer function 
-- Select Mutator(s) for the set of rounds
local function SurvivalEvent_MutatorRandomizer(mutatorCount)

	local totalMutators = table.getn(mutatorList)
	local selectedList = {}
	
	print "selecting mutators"
	-- randomly select mutators until a unique list of length mutatorCount is created
	if mutatorCount <= totalMutators then
		math.randomseed(Time.Now())
		
		while table.getn(selectedList) != mutatorCount do
			local rand = random(1,totalMutators)
			local found = false
			
			if rand < totalMutators then
				for id = 1, table.getn(selectedList) do
					if mutatorList[rand] == selectedList[id] then
						found = true
					
					end
				
				end
				
				if not found then
					table.insert(selectedList, mutatorList[rand])
				
				end
			
			end
		
		end
		
		-- Apply selected Mutators
		local totalMutatorsSelected = table.getn(selectedList)
		
		if totalMutatorsSelected > 1 then
			LuaGlobalEvent("notifyPluralMutators")
		else
			LuaGlobalEvent("notifyMutators")
		end
		
		
		for id = 1, totalMutatorsSelected do
			Game.AddMutator(selectedList[id])
		
		end		
	
	end

end

I’ll look into the Mutator script to check how it really works, as I don’t remember now myself.
You can see in the code that it:

  • draws a random mutator

    • local rand = random(1,totalMutators)

  • till it has appropriate number of them for the wave

    • while table.getn(selectedList) != mutatorCount do

  • also checks if mutators don’t repeat 
    •  		if not found then
 			table.insert(selectedList, mutatorList[rand])

You can show why 1/27+1/26+1/25+1/24+1/23 cannot be a correct answer:

  • let’s say we have 27 mutators in a wave -> what’s the probability of getting Unstoppable in a single wave?

  • with @banana_peel’s formula (was 5/27 in previous case ) it’s 27 / 27 = 100% <- ok

  • with your formula it’s:

    • 1/27 + 1/26 + … + 1/2 + 1/1 ~ 3.89 > 1 = 100%

      • the answer doesn’t make sense because you get a number bigger than 1 which means there’s must be something wrong here.

A similar mistake that was made in this post [Feedback] Concerns about drop chance of some MI legendaries

It’s hard for me to explain it simply but when you look at these mutator sequences:
A, B, C, D, E
you say it’s 1/26 for B. And it’s true that when A was already chosen, B has 26 options.

But these events of selecting A and B are not independent as you said and
B is 1/26 to be Unstoppable only if A was not Unstoppable to begin with.

You lost all these events / Mutator sequences where A was Unstoppable.
Then B has 0% chance to be Unstoppable and this has to be included:

Probability of A being Unstoppable = 1/27

Probability of B being Unstoppable =
= 1/26 * (prob A was not Unstoppable) + 0% * (prob A is Unstoppable) =
= 1/26 * 26/27 + 0% * 1/27 =
= 1/27
(using https://en.wikipedia.org/wiki/Conditional_probability)

Probability of C being Unstoppable = 1/25 * (probability A,B were not Unstoppable) 25 / 27 = 1/27

Or in another way straightforward way without conditional probability:

  • we have 27*26*25*24*23 sequences (A,B,C,D,E)

    • how many of them have B=Unstoppable?

  • Those that start with A=Not Unstoppable (26 options), then Unstoppable (1 option) then whatever:

    • 26*1*25*24*23

  • probability of B being Unstoppable is then:

    • (26*1*25*24*23) / (27*26*25*24*23) = (26*1) / (27*26) = 1/27

It took me some time to wrap my head around this :laughing:
@grey-maybe By the way your previous answer (10/27) would be correct if mutators could not repeat between wave 1 and 2.

so I agree with Banana’s answer:

  • with a separate wave prob to get Unstoppable is 5/27
  • so to get Unstoppable in the whole run prob is 1-(1-5/27)^2
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