//------------------------------------------------------------------------------
//
//  Formula Name:    Donchian Channel
//  Author/Uploader: R. Bertematto 
//  E-mail:          
//  Date/Time Added: 2003-06-09 22:58:40
//  Origin:          
//  Keywords:        donchian channel
//  Level:           basic
//  Flags:           indicator
//  Formula URL:     http://www.amibroker.com/library/formula.php?id=285
//  Details URL:     http://www.amibroker.com/library/detail.php?id=285
//
//------------------------------------------------------------------------------
//
//  This plots a Donchian Channel, similar to a Bollinger Band but based on
//  highs and lows. Good for support/resistance.
//
//------------------------------------------------------------------------------

// Plots a 20 period Donchian channel

pds=20;
DonchianUpper =HHV(Ref(H,-1),pds);
DonchianLower = LLV(Ref(L,-1),pds);
DonchianMiddle = (DonchianUpper+DonchianLower)/2;


Plot(DonchianUpper,"DU",colorBlue,styleLine);
Plot(DonchianMiddle,"DM",colorGreen,styleLine);
Plot(DonchianLower,"DL",colorRed,styleLine);