Module:Average change

local p = {}

-- Main function to calculate average change
function p.main(displayType, omitOperator, ...)
    -- Collect all variable arguments into a table
    local params = {...}
    
    -- Filter out nil values and convert to numbers
    local values = {}
    for _, v in ipairs(params) do
        v = tonumber(v)
        if v then
            table.insert(values, v)
        end
    end
    
    -- Error if fewer than 2 valid values
    if #values < 2 then
        return 'Error: Insufficient parameters'
    end
    
    -- Calculate changes
    local changes = {}
    for i = 1, #values - 1 do
        if displayType == "percent" then
            table.insert(changes, ((values[i + 1] - values[i]) / values[i]) * 100)
        else
            table.insert(changes, values[i + 1] - values[i])
        end
    end
    
    -- Calculate average change
    local sum = 0
    for _, change in ipairs(changes) do
        sum = sum + change
    end
    
    local avgChange = sum / #changes
    local formattedChange = string.format("%.2f", avgChange)
    
    -- Omit the operator if specified
    if omitOperator == "yes" then
        formattedChange = string.gsub(formattedChange, "^%-", "")
    end
    
    return formattedChange
end

return p