attempt to call global 'createMap' (a nil value)?

This has happened to me more than once to simple and complex scripts for reasons i do not know.

I have a script trying to call a function and i get an error trying to call the function.

Workspace.Script:8: attempt to call global 'createMap' (a nil value)

I do not know why this is happening. Here is the code.

    math.randomseed(tick())
    local Seed = math.random(0,999999)
    local MaxTest = {}
    local MinTest = {}
    local Max = 0
    local Min = 0

    createMap(50,50,10,10,5,2.5)

 function createMap(Width, Height, Scale, Octives, Persistance, Lacunarity)
    local cordX = {}
    for x = 0,127 do
        local cordY = {}
        cordX[x] = cordY
        for y = 0,127 do
            local Amplitude = 1
            local Frequency = 1
            local noiseHeight = 0       

            for i=0, Octives do
                local SampleX = x/Scale * Frequency
                local SampleY = y/Scale * Frequency

                local PerlinValue = math.noise(SampleX,SampleY)
                noiseHeight = noiseHeight + PerlinValue * Amplitude
                Amplitude = Amplitude * Persistance
                Frequency = Frequency * Lacunarity
            end
            cordY[y] = noiseHeight
        end
        table.insert(MaxTest,1,math.max(unpack(cordX[x])))
        table.insert(MinTest,1,math.min(unpack(cordX[x])))
        wait()
    end
    Max = math.max(unpack(MaxTest))
    Min = math.max(unpack(MinTest))
end