Get the dot product of any MxN matrices

dot-product.lua

-- Utility functions for matrix.dot
local function dotScalar1dVector(scalar, v1)
	local outputVector = {}
	for i = 1, #v1, 1 do
		outputVector[i] = v1[i] * scalar
	end
	return matrix(outputVector)
end

local function dotScalar2dVector(scalar, v1)
	local outputVector = {}
	for i = 1, #v1, 1 do
		outputVector[i] = dotScalar1dVector(scalar, v1[i])
	end
	return matrix(outputVector)
end

local function dot1dVector1dVector(v1, v2)
	if #v1 ~= #v2 then 
		error("Shape error: #m1 ~= #m2, " .. #v1 .. "~=" .. #v2, nil)
	end
	local sum = 0
	for i = 1, #v1, 1 do
		sum = sum + v1[i] * v2[i]
	end
	return sum
end

local function dot1dVector2dVector(v1, v2)
	if #v1 ~= #v2[1] then 
		error("Shape error: m1 columns ~= m2 rows, " .. #v1 .. "~=" .. #v2[1], nil)
	end
	local layerOutput = {};
	for i = 1, #v2, 1 do
		layerOutput[i] = dot1dVector1dVector(v1, v2[i])
	end
	return layerOutput
end

local function dot2dVector2dVector(v1, v2)
	if #v1[1] ~= #v2 then 
		error("Shape error: m1 columns ~= m2 rows, " .. #v1[1] .. "~=" .. #v2, nil)
	end
	local result = {}
	for i = 1, #v1, 1 do
		for j = 1, #v2[1], 1 do
			local v1Rowi = v1[i]
			local v2Colj = transpose(v2)[j]
			if type(result[i]) == "nil" then result[i] = {} end
			result[i][j] = dot1dVector1dVector(v1Rowi, v2Colj)
		end
	end
	return result
end

function transpose(v1)
	local transposedBoard = {}
	for i = 1, #v1[1], 1 do
		local newRow = {}
		for j = 1, #v1, 1 do
			newRow[#newRow+1] = v1[j][i]
		end
		transposedBoard[#transposedBoard+1] = newRow
	end
	return transposedBoard
end

--// matrix.dot ( m1, m2 )
-- returns the dot product of two vectors
function matrix.dot(v1, v2)
	if type(v1) == "number" and type(v2) == "table" and type(v2[1]) == "number" then
		return dotScalar1dVector(v1, v2)
	elseif type(v1) == "number" and type(v2) == "table" and type(v2[1]) == "table" and type(v2[1][1]) == "number" then
		return dotScalar2dVector(v1, v2)
	elseif type(v1) == "table" and type(v1[1]) == "number" and type(v2) == "table" and type(v2[1]) == "number" then
		return dot1dVector1dVector(v1, v2)
	elseif type(v1) == "table" and type(v1[1]) == "number" and type(v2) == "table" and type(v2[1]) == "table" and type(v2[1][1]) == "number" then
		return dot1dVector2dVector(v1, v2)
	elseif type(v1) == "table" and type(v1[1]) == "table" and type(v1[1][1]) == "number" and type(v2) == "table" and type(v2[1]) == "table" and type(v2[1][1]) == "number" then
		return dot2dVector2dVector(v1, v2)
	end
	error("Not valid matrix inputs")
end