Expert Advisor Programming by Andrew R. Young

Custom Indicators and Scripts
If your indicator is drawn in a separate window (such as an oscillator), and you'd like to add levels to
indicate overbought or oversold levels (such as in the Stochastic or RSI indicators), or the zero level
(such as in the CCI indicator), you can use the SetLevelStyle() and SetLevelValue() functions.
See the MQL Reference under Custom Indicators for more information.
You may also want to specify a short indicator name to be displayed in the top left corner of the
indicator window. Use the IndicatorShortName() function to set this value. The only parameter is a
text string that will appear in the top left corner of the indicator window, as well as in the data
window.
Using Descriptive Buffer Names
Here is our updated indicator code. Note that we've renamed the buffer arrays to be more descriptive
as to their actual function. We've changed the second parameter of the SetIndexBuffer() functions
to reflect the new buffer names. We've also added SetIndexLabel() for each line to display
descriptive names in the Data Window.
//---- buffers
double EMA[];
double UpperBand[];
double LowerBand[];
//+------------------------------------------------------------------+
//| Custom indicator initialization function |
//+------------------------------------------------------------------+
int init()
{
//---- indicators
SetIndexStyle(0,DRAW_LINE);
SetIndexBuffer(0,EMA);
SetIndexLabel(0,"EMA");
SetIndexStyle(1,DRAW_LINE);
SetIndexBuffer(1,UpperBand);
SetIndexLabel(1,"UpperBand");
SetIndexStyle(2,DRAW_LINE);
SetIndexBuffer(2,LowerBand);
SetIndexLabel(2,"LowerBand");
//----
return(0);
}
We've renamed our buffer arrays from the default names (ExtMapBuffer) to more descriptive ones.
EMA[] will be our buffer for the center line, and UpperBand[] and LowerBand[] will be the upper
and lower bands respectively.
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