//|                                                        BB-HL.mq4 |
//|                                Copyright © 2005, David W. Thomas |
//|                                           mailto:davidwt@usa.net |
//+------------------------------------------------------------------+
#property copyright "Copyright © 2005, David W. Thomas"
#property link      "mailto:davidwt@usa.net"

#property indicator_chart_window
#property indicator_buffers 3
#property indicator_color1 MediumSeaGreen
#property indicator_color2 MediumSeaGreen
#property indicator_color3 MediumSeaGreen

//---- input parameters
extern int       Per=20;
extern double    nDev=2.0;

//---- buffers
double MABuffer[];
double UpperBandBuffer[];
double LowerBandBuffer[];
double DevsBuffer[];

//+------------------------------------------------------------------+
//| Custom indicator initialization function                         |
//+------------------------------------------------------------------+
int init()
{
   IndicatorBuffers(4);
//---- indicators
SetIndexStyle(0,DRAW_LINE);
SetIndexBuffer(0,MABuffer);
   SetIndexDrawBegin(0,Per);
SetIndexEmptyValue(0, 0.0);
SetIndexStyle(1,DRAW_LINE);
SetIndexBuffer(1,UpperBandBuffer);
   SetIndexDrawBegin(1,2*Per);
SetIndexEmptyValue(1, 0.0);
SetIndexStyle(2,DRAW_LINE);
SetIndexBuffer(2,LowerBandBuffer);
   SetIndexDrawBegin(2,2*Per);
SetIndexEmptyValue(2, 0.0);
SetIndexBuffer(3,DevsBuffer);
//----
   string short_name="BB-HL(" + Per + "," + DoubleToStr(nDev, 1) + ")";
   IndicatorShortName(short_name);
return(0);
}
//+------------------------------------------------------------------+
//| Custor indicator deinitialization function                       |
//+------------------------------------------------------------------+
int deinit()
{
//---- 

//----
return(0);
}
//+------------------------------------------------------------------+
//| Custom indicator iteration function                              |
//+------------------------------------------------------------------+
int start()
{
int    limit;
int    counted_bars = IndicatorCounted();
double d1, d2, ma;
//---- last counted bar will be recounted
if (counted_bars>0) counted_bars--;
limit = Bars - counted_bars;
//---- simple moving average and deviations
for (int i=limit; i>=0; i--)
{
ma = iMA(NULL, 0, Per, 0, MODE_SMA, PRICE_MEDIAN, i);
d1 = High[i] - ma;
d1 *= d1;
d2 = Low[i] - ma;
d2 *= d2;
MABuffer[i] = ma;
DevsBuffer[i] = MathMax(d1, d2);
}
//---- compute the bands
UpperBandBuffer[limit] = 0.0;
LowerBandBuffer[limit] = 0.0;
for (i=limit; i>=0; i--)
{
d1 = 0;
for (int j=i; j<i+Per; j++)
d1 += DevsBuffer[j];
d1 /= Per;
d2 = nDev * MathSqrt(d1);
ma = MABuffer[i];
UpperBandBuffer[i] = ma + d2;
LowerBandBuffer[i] = ma - d2;
}
return(0);
}
//+------------------------------------------------------------------+