How can I count the frequency of values in a list? [closed]

So, this may be a terrible terrible setup because its my first time trying one. But I am trying to do map voting and when the player votes their userId gets added to a table with the map they voted. and to get the frequency I tried doing this

local function countFreq(tab)
    local freq = {};
    for _, v in ipairs(tab) do
        freq[v] = (freq[v] or 0) + 1;
    end
    return freq;
end

Always returns nil even if there is votes, and or duplicate votes.