Graph Prototype 1 - displays a few graphs in a demo graphing window

graph.lua

--[[
PUBLIC DOMAIN
Where this designation is not recognized, you are
permitted to copy, modify, and distribute this code
without restriction.

Lucien Greathouse
(LPGhatguy)
]]

colors = {
	{200, 50, 50},
	{30, 180, 30},
	{50, 50, 200}
}

setmetatable(colors, {
	__index = function(self, key)
		return {255, 255, 255}
	end
})

local render = function(fs, x_range, y_range, canvas_size)
	local canvas_w, canvas_h = canvas and unpack(canvas_size)
	canvas_w = canvas_w or 400
	canvas_h = canvas_h or 400

	local scale_x = canvas_w / (x_range[2] - x_range[1])
	local scale_y = canvas_h / (y_range[2] - y_range[1])
	local step = 0.05

	local canvas = love.graphics.newCanvas(canvas_w, canvas_h)

	love.graphics.setCanvas(canvas)

	love.graphics.rectangle("line", 0, 0, canvas_w, canvas_h)

	love.graphics.scale(1, 1)
	love.graphics.translate(math.abs(x_range[1]) * scale_x, math.abs(y_range[1]) * scale_y)

	for index, f in pairs(fs) do
		love.graphics.setColor(colors[index])
		for x = x_range[1], x_range[2], step do
			love.graphics.line(x * scale_x, -f(x) * scale_y, (x + step) * scale_x, -f(x + step) * scale_y)
		end
	end

	love.graphics.setColor(255, 255, 255)

	love.graphics.line(0, y_range[2] * scale_y, 0, y_range[1] * scale_y)
	love.graphics.line(x_range[2] * scale_x, 0, x_range[1] * scale_x, 0)

	for x = x_range[1], x_range[2] do
		love.graphics.line(x * scale_x, 4, x * scale_x, -4)
		love.graphics.print(tostring(x), x * scale_x + 2, 2)
	end

	for y = y_range[1], y_range[2] do
		love.graphics.line(-4, -y * scale_y, 4, -y * scale_y)
		love.graphics.print(tostring(y), 2, -y * scale_y + 2)
	end

	love.graphics.setCanvas()

	return canvas
end

local result

function love.load()
	result = render({
		function(x)
			return x^2
		end,

		function(x)
			return x^3
		end,

		function(x)
			return math.log(x)
		end,

		function(x)
			return x
		end
	}, {-5, 5}, {-5, 5})
end

function love.draw()
	love.graphics.draw(result, 100, 100)
end