table confusion

--love.load
xy = {}
table.insert(xy, {x = 200, y = 200})
table.insert(xy, {x = 600, y = 200})
table.insert(xy, {x = 600, y = 400})
table.insert(xy, {x = 200, y = 400})

linur = {}

--love.update

for i = 1, 4 do
    linur[i].nalaegd = pyth(mx, xy[i].x, my, xy[i].y)
end

function pyth(x1, x2, y1, y2)
    return math.sqrt((x1 - x2)*(x1 - x2) + (y1 - y2)*(y1 - y2))
end