<?php
defined('BASEPATH') or exit('No direct script access allowed');

function variation($data, $i, $f, $t, &$dMin, &$dMax,  &$tVar, &$tVar0)
{
    $tVar[] = $f['cost'];
    $trend = $t[$f['time']][2];
    $delta = $f['cost'] - $trend;
    $variation = stats_variance($tVar);
    if ($delta>$dMax) $dMax = $delta;
    if ($delta<$dMin) $dMin = $delta;
    $tVar0[$f['time']] = $variation;

    /* {
    "travel_date":"2020-05-10 14:54:04+00",
    "cost":"12",
    "location_start_lat":"1.319292",
    "location_start_lng":"103.9126091",
    "location_end_lat":"1.316269",
    "location_end_lng":"103.977615",
    "origin":"Central East - Eunos",
    "destination":"Far East - Changi",
    "c":"#5555ff"} */
    //if ($i<5) error_log(json_encode($t));
    return [$trend, $delta, $variation];
}