How to randomize a table

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#1

I am using a table of position for a Mine Spawner in a tower defense game.

I call the table every 5 seconds to give me a random position on the Mob Path.

Currently the table plays from first to last everytime its called, resulting in the mines spawning in the same position every time.

How do I randomize the table when it is called?

This is the parts of the script involving the table:

Summary 
local function newPoint()
	for _, pointList in pairs(mathPoints) do
		if #pointList > 2 then
			local firstPoint = pointList[math.random(#pointList)].Position

			local isStraight = true

			for i, point in ipairs(pointList) do
				if i > 1 then
					local direction = (point.Position - firstPoint).Unit

					local dotProduct = math.abs(direction:Dot((pointList[i-1].Position - firstPoint).Unit))

					if dotProduct < .99 then -- not within 2 degrees of each other, so not straight line
						isStraight = false
						break;
					end

				end

			end

			if isStraight then
				--get random location between 2 points
				print(pointList)
				minePosition = firstPoint + (pointList[#pointList].Position - firstPoint) * math.random()

				break;
			end

		end

	end
end


while true do 
	--spawn mine every 5 seconds
	wait(1)
	
	if minePosition then
		print(minePosition)
		local newMine = mine:Clone()
		newMine.Parent = tower
		
		newMine.PrimaryPart.Position = minePosition 
	end
	newPoint()
end
2 Likes
#2

Please try researching a bit before creating a topic next time. Hopefully this topic can help.

1 Like
#3

I actually tried this before posting :wink:

local function shuffle(tableToShuffle: table): table
		local ShuffledTable = {}

		for Index = 1, #mathPointsdo
			local RandomIndex = math.random(#mathPoints)
			table.insert(ShuffledTable , mathPoints[RandomIndex])
			table.remove(mathPoints, RandomIndex)
		end
		
		print(ShuffledTable)
		
		return ShuffledTable 
	end
	
	shuffle(mathPoints)

It doesn’t seem to work for me? print(ShuffledTable)
image

#4

Use a Fisher-Yates shuffle:

Code:

local function shuffle(t)
	local j, temp
	for i = #t, 1, -1 do
		j = math.random(i)
		temp = t[i]
		t[i] = t[j]
		t[j] = temp
	end
	
	return t
end

shuffle(mathPoints)
print(mathPoints)
1 Like
#5

This may be an issue with the structure of my table, but it doesn’t seem to work either.

image
image614×544 33.7 KB

#6

why dont you just randomise the index?

local array = {1, 2, 3, 4, 5}
local index = math.random(1, #array)

print(array[index])
#7

Sorry but I don’t really understand so well how tables work.

How would I incorporate this into my table?

for _, pointList in pairs(mathPoints) do
		if #pointList > 2 then
			local firstPoint = pointList[math.random(#pointList)].Position

			local isStraight = true

			for i, point in ipairs(pointList) do
				if i > 1 then
					local direction = (point.Position - firstPoint).Unit

					local dotProduct = math.abs(direction:Dot((pointList[i-1].Position - firstPoint).Unit))

					if dotProduct < .99 then -- not within 2 degrees of each other, so not straight line
						isStraight = false
						break;
					end

				end

			end

			if isStraight then
				--get random location between 2 points
				minePosition = firstPoint + (pointList[#pointList].Position - firstPoint) * math.random()

				break;
			end

		end

	end

The mathPoints table needs randomized before this section of code, or within the for do loop if possible?

#8

I’m pretty sure the temp variable isn’t needed in Lua because it’s possible to change/swap 2 values at once:

local function shuffle(t)
	for i = #t, 1, -1 do
		local j = math.random(i)
		t[i], t[j] = t[j], t[i]
	end
end

shuffle(mathPoints)
print(mathPoints)

Also as @TaxFraudBruh mentioned you can just randomize the indexes when picking the items:

local availableIndexes = {}
for i = 1, #mathPoints do table.insert(availableIndexes, i) end

for i = 1, #mathPoints do
	local index = availableIndexes[math.random(#availableIndexes)]
	print(index, mathPoints[index])
end
1 Like
#9

This returns the same table as @Katrist’s solution

#10

I know, I just mentioned that the temp variable wasn’t needed and the function size could be reduced.

1 Like
#11

This wouldn’t randomize it, but this should swap the order of the table right?

if sortOrder == "a" then
		table.sort(mathPoints, function(a,b)
			return a[2] > b[2]
		end)
		print("A", mathPoints)
		sortOrder = "b"
	else
		table.sort(mathPoints, function(a,b)
			return a[2] < b[2]
		end)
		print("B", mathPoints)
		sortOrder = "a"
	end

For some reason this returns the same table.
image