Drawing a Matrix - lua

Question

Im trying to generate a random map using a matrix but I dont really know how. Here is the
function for the matrix. wMap and hMap are the width and height, and mapSprites is a table containing some ground sprites. Also how can I draw the matrix? Im sorry if this is too much of a question, but Im really in need for some help
function buildMap(wMap, hMap)
for i = 1, wMap do
mt[i] = {}
for j = 1, hMap do
mt[i][j] = math.random(mapSprites)
end
end
end

Answer 1

Generating a random map in any programming language will utilize two core concepts: The language's random function and nested for loops, two for the case of a map/matrix/2d array.
The first problem, is you may or may not have mt initialized outside the function. This function assumes the variable exists outside of the function and each time the function is called it will overwrite mt (or initialize it for the first function call) with random values.
The second problem, the width, wMap, and height, hMap, of the map are in the wrong order, as maps/matrices/2d arrays first iterate over the height (y dimension) and then the width (x dimension).
The last problem, mapSpripes also has to be declared outside the function (which is not clear with your code snippet), which will be the highest possible value the random function can generate. You can read more about math.random here: http://lua-users.org/wiki/MathLibraryTutorial
Consider this function I wrote that makes those adjustments as well as has some additional variables for the minimum and maximum random value. Of course, you can remove these to have it fit your intended purposes.
function buildMap(wMap, hMap)
local minRand = 10
local maxRand = 20
for y = 1, hMap do
matrix[y] = {}
for x = 1, wMap do
matrix[y][x] = math.random(minRand, maxRand)
end
end
end
I suggest you use this function as inspiration for your future iteratins. You can make minRand and maxRand parameters or make matrix a returned value rather than manipulating an already declared matrix value outside of the function.
Best of luck!
EDIT:
Regarding your second question. Look back at the section I wrote about nested for loops. This will be crucial to "drawing" your map. I believe you have the building blocks to resolve this issue yourself as there isn't enough context provided about what "drawing" looks like. Here is a fundamentally similiar function, based on my previous function, on printing the map:
function printMap(matrix)
for i = 1, #matrix do
for j = 1, #matrix[i] do
io.write(matrix[i][j] .. " ")
end
io.write("\n")
end
end

Answer 2

For choosing random sprite, I recommend you to create a table of sprites and then save index of sprite in matrix. Then you can draw it in same loop, but now, you will iterate over matrix and draw sprite based on sprite index saved in matrix in position given by matrix position (x and y in loop) times size of sprite.
local sprites, mt = {}, {}
local spriteWidth, spriteHeight = 16, 16 -- Width and height of sprites
function buildMap(wMap, hMap)
mt = {}
for i = 1, wMap do
mt[i] = {}
for j = 1, hMap do
mt[i][j] = math.random(#sprites) -- We choose random sprite index (#sprites is length of sprites table)
end
end
end
function love.load()
sprites = {
love.graphics.newImage('sprite1.png'),
love.graphics.newImage('sprite2.png'),
-- ...
}
buildMap()
end
function love.draw()
for y, row in ipairs(mt) do
for x, spriteIndex in ipairs(row) do
-- x - 1, because we want to start at 0, 0, but lua table indexing starts at 1
love.graphics.draw(sprites[spriteIndex], (x - 1) * spriteWidth, (y - 1) * spriteHeight)
end
end
end