lua:90: attempt to index field '?' (a nil value)

Question

I cannot get my 2 dimensional variable to be recognized correctly when I call it. When I print it, it seems to work fine, but when I attempt to call it from within a function it goes bananas on me.

Here is my code:

math.randomseed(os.time())
math.random(); math.random(); math.random()
--init
local t = ""
--t == type
local year = 2014
--year is placeholder with no real value.
local i = 1
local x = 0
local y = 0
local z = 0
local o = 0
--
local l = 0
local l1 = 0
local l2 = 0
--
local h = 1
--Junk Variables
local month = {"01", "02", "03", "04", "05", "06", "07", "08", "09", "10", "11", "12"}
local days = {0, 0, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
--Days linked to months, weeks come as calculated
local m = 1
--"m" is the real month value to be used within the code as the literal value.
fd = {}          -- create the matrix
    for y=1,5 do
      fd[y] = {}     -- create a new row
      for z=1,5 do
        fd[y][z] = 0
      end
    end
--fd = Family/Day
na = {1, 2, 3, 4 ,5}
--numbers not allocated for the day
fv = {}
--[12][days[m]][5]
--final value to be printed literally into string of txt file.
local s = ""
--string variable
io.write("Please enter a month (ONLY USE NUMBERS)")
io.flush()
m=io.read()
io.write("Please enter a chore creation type (daily, weekly, monthly [Case sensitive])")
t=io.read()
--
m = tonumber(m)
--
for y=1,12 do
    fv[y] = {}
    for z=1,days[m] do
        fv[y][z] = {}
        for o=1,5 do
            fv[y][z][o] = 0
        end
    end
end
--
if t == "daily" then
    local f,err = io.open("ChoreDaily.txt","w")
    if not f then return print(err) end
    f:write("")
    --
    repeat
        i = 0
        y = 0
        print(">>")
        repeat
            if h <= days[m] then
            --
                repeat
                    if h <= days[m] then
                        --
                        os.execute("cls")
                        l1 = math.random(1,2)
                        l2 = math.random(3,4)
                        l = math.random(l1,l2)
                        repeat
                            o = math.random(1,5)
                            l = l-1
                        until l == 0
                        --
                        if y == 0 then
                            --
                            if na[o] > 0 then
                                if x < 4 then
                                    s = s .. tostring(na[o]) .. ", "
                                elseif x >= 4 then
                                    s = s .. tostring(na[o])
                                end
                                fd[x][y] = na[o] -- this is the problem.
                                na[o] = 0
                                x = x+1
                                print("!")
                            end
    --

I think it's pretty obvious what I am attempting to make overall, but it's a chore list creator. pretty primitive and I was hoping I could do it all myself, but unfortunately if I can't utilize 2 dimensional variables I'm not going to be able to go much further.

There are some unused variables and whatnot hanging around. I plan to get rid of those later.

Answer 1

x is initialized as 0, and is not changed before you try to access fd[x][y]. But the valid index of the table fd is from 1 to 5, which means fd[x] is nil here, you can't access fd[x][y].