(PECL trader >= 0.2.0)
trader_var — Variance
$real
[, int $timePeriod
[, float $nbDev
]] ) : array
real锟斤拷锟斤拷锟斤拷锟斤拷锟介。
timePeriodNumber of period. Valid range from 2 to 100000.
nbDev
Returns an array with calculated data or false on failure.