Explanation of Heiken Ashi

[[Deleted]]

Hi, I am a mql4 newbie.

I would like to understand the Heiken Ashi code. More precisely, I would like to understand how the DRAW HISTOGRAM works and how can we build a candle stick.

The code is the following :

#property copyright "Copyright ｩ 2004, MetaQuotes Software Corp."
#property link "http://www.metaquotes.net"

#property indicator_chart_window
#property indicator_buffers 4
#property indicator_color1 Red
#property indicator_color2 White
#property indicator_color3 Red
#property indicator_color4 White
#property indicator_width1 1
#property indicator_width2 1
#property indicator_width3 3
#property indicator_width4 3

//----
extern color color1 = Red;
extern color color2 = White;
extern color color3 = Red;
extern color color4 = White;
//---- buffers
double ExtMapBuffer1[];
double ExtMapBuffer2[];
double ExtMapBuffer3[];
double ExtMapBuffer4[];
//----
int ExtCountedBars=0;
//+------------------------------------------------------------------+
//| Custom indicator initialization function |
//|------------------------------------------------------------------|
int init()
{
//---- indicators
SetIndexStyle(0,DRAW_HISTOGRAM, 0, 1, color1);
SetIndexBuffer(0, ExtMapBuffer1);
SetIndexStyle(1,DRAW_HISTOGRAM, 0, 1, color2);
SetIndexBuffer(1, ExtMapBuffer2);
SetIndexStyle(2,DRAW_HISTOGRAM, 0, 3, color3);
SetIndexBuffer(2, ExtMapBuffer3);
SetIndexStyle(3,DRAW_HISTOGRAM, 0, 3, color4);
SetIndexBuffer(3, ExtMapBuffer4);
//----
SetIndexDrawBegin(0,10);
SetIndexDrawBegin(1,10);
SetIndexDrawBegin(2,10);
SetIndexDrawBegin(3,10);
//---- indicator buffers mapping
SetIndexBuffer(0,ExtMapBuffer1);
SetIndexBuffer(1,ExtMapBuffer2);
SetIndexBuffer(2,ExtMapBuffer3);
SetIndexBuffer(3,ExtMapBuffer4);
//---- initialization done
return(0);
}
//+------------------------------------------------------------------+
//| Custom indicator deinitialization function |
//+------------------------------------------------------------------+
int deinit()
{
//---- TODO: add your code here

//----
return(0);
}
//+------------------------------------------------------------------+
//| Custom indicator iteration function |
//+------------------------------------------------------------------+
int start()
{
double haOpen, haHigh, haLow, haClose;
if(Bars<=10) return(0);
ExtCountedBars=IndicatorCounted();
//---- check for possible errors
if (ExtCountedBars<0) return(-1);
//---- last counted bar will be recounted
if (ExtCountedBars>0) ExtCountedBars--;
int pos=Bars-ExtCountedBars-1;
while(pos>=0)
{
haOpen=(ExtMapBuffer3[pos+1]+ExtMapBuffer4[pos+1])/2;
haClose=(Open[pos]+High[pos]+Low[pos]+Close[pos])/4;
haHigh=MathMax(High[pos], MathMax(haOpen, haClose));
haLow=MathMin(Low[pos], MathMin(haOpen, haClose));
if (haOpen<haClose)
{
ExtMapBuffer1[pos]=haLow;
ExtMapBuffer2[pos]=haHigh;
}
else
{
ExtMapBuffer1[pos]=haHigh;
ExtMapBuffer2[pos]=haLow;
}
ExtMapBuffer3[pos]=haOpen;
ExtMapBuffer4[pos]=haClose;
pos--;
}
//----
return(0);


I have underlined the lines that I do not understand, if someone can give me a reference or an explanation, it would be great. Thanks by advance.

[okwh]

one candle need 4 values: h, l, O, C,
draw in 2 HISTOGRAM, one need h and l, one need O and C.
and 4 colors:
if H>L draw in one color
if H<L draw in one color
if O>P draw in one color
if O<P draw in one color