input numDevDn = -1.0;
input numDevUp = 1.0;
input timeFrame = {default DAY, WEEK, MONTH};

def cap = getAggregationPeriod();
def errorInAggregation =
    timeFrame == timeFrame.DAY and cap >= AggregationPeriod.WEEK or
    timeFrame == timeFrame.WEEK and cap >= AggregationPeriod.MONTH;
assert(!errorInAggregation, "timeFrame should be not less than current chart aggregation period");

def yyyyMmDd = getYyyyMmDd();
def periodIndx;
switch (timeFrame) {
case DAY:
    periodIndx = yyyyMmDd;
case WEEK:
    periodIndx = Floor((daysFromDate(first(yyyyMmDd)) + getDayOfWeek(first(yyyyMmDd))) / 7);
case MONTH:
    periodIndx = roundDown(yyyyMmDd / 100, 0);
}
def isPeriodRolled = compoundValue(1, periodIndx != periodIndx[1], yes);

def volumeSum;
def volumeVwapSum;
def volumeVwap2Sum;

if (isPeriodRolled) {
    volumeSum = volume;
    volumeVwapSum = volume * vwap;
    volumeVwap2Sum = volume * Sqr(vwap);
} else {
    volumeSum = compoundValue(1, volumeSum[1] + volume, volume);
    volumeVwapSum = compoundValue(1, volumeVwapSum[1] + volume * vwap, volume * vwap);
    volumeVwap2Sum = compoundValue(1, volumeVwap2Sum[1] + volume * Sqr(vwap), volume * Sqr(vwap));
}
def price = volumeVwapSum / volumeSum;
def deviation = Sqrt(Max(volumeVwap2Sum / volumeSum - Sqr(price), 0));

def VWAP = price;

def VWAP_Upper = price + numDevUp * deviation;
def VWAP_Lower = price + numDevDn * deviation;

def SignalEMA = movAvgExponential (3);

def VWAP_StrongBull = SignalEMA crosses above VWAP_Upper within 5 bars;
plot VWAP_Num = if VWAP_StrongBull is true then 2 else 0;
AssignBackgroundColor(if VWAP_Num == 2 then Color.BLUE else Color.Black);