Question

I have 2 different 2d Arrays set up in lua. The first loop

bubbleMat = {}                              --Set Up Table called bubbleMat
for i = 1, 10 do
    bubbleMat[i] = {}                           --1D table with 10 components

    for j = 1, 13 do
        bubbleMat[i][j] = bubbleClass.new( (i*62) - 62, (j*62) - 62 )   --2D Table with 10x13 Matrix each cell given a coordinate as it is iterated through the loop
    end
end

With this array i can print value of any position in the array to the console with

print(bubbleMat[x][y]) 

for whatever numbers of x and y

The second array for some reason does not work. The second array is as follows

 bubbleMat = {}                             --Set Up Table called     bubbleMat
for j = 1, 13 do
    for i = 1, 10 do
        bubbleMat[i] = {}
        --bubbleMat[i][j] = {}
            if j%2 == 0 then
                bubbleMat[i][j] = bubbleClass.new( (i*62) - 31, (j*62) - 62 )
            else
                bubbleMat[i][j] = bubbleClass.new( (i*62) - 62, (j*62) - 62 )
            end
    end
end

print(bubbleMat)

I am unsure why I cannot index the second array

this is the following error I get in the console

 attempt to index field '?' (a nil value)

Thanks in advance for any help.

Basically i want to display a grid of bubbles stored in a 2d array in the following pattern

0   0    0    0    0    0    0    0    0    0
  0    0    0    0    0    0    0    0    0

as opposed to having the bubbles in the next line positioned directly underneath

Answer 1

Loop for j is outside and loop for i is inside. This is not necessarily false, but unusual.

However, bubbleMat[i] is initialized to {} in the innermost loop, which is clearly wrong.

Either move that initialization into the outermost loop, or use this syntax :

bubbleMat[i] = bubbleMat[i] or {}