【MQL4】Williams%R(iWPR)が-80/-20ラインに到達した瞬間だけを矢印表示するインジケーターの作り方(既刊EAの『戻り確認』より早いサインとして使う設計)

//+------------------------------------------------------------------+
//|                                 WprZoneEntryArrow.mq4             |
//|                     Copyright 2026, FX-EA System Project Creator |
//|                        https://creator.fx-ea-system-project.com/ |
//+------------------------------------------------------------------+
#property copyright "Copyright 2026, FX-EA System Project Creator"
#property link      "https://creator.fx-ea-system-project.com/"
#property version   "1.00"
#property strict
#property indicator_separate_window
#property indicator_buffers 2
#property indicator_color1 DeepSkyBlue
#property indicator_color2 OrangeRed
#property indicator_minimum -100
#property indicator_maximum 0

input int    InpPeriod         = 14;    //Williams%Rの計算期間
input double InpOversold       = -80.0; //売られすぎライン
input double InpOverbought     = -20.0; //買われすぎライン
input int    InpArrowGapPoints = 10;    //ラインから矢印を離すポイント数

double OversoldArrow[];
double OverboughtArrow[];

//+------------------------------------------------------------------+
//| Custom indicator initialization function                         |
//+------------------------------------------------------------------+
int OnInit()
  {
   SetIndexBuffer(0, OversoldArrow);
   SetIndexStyle(0, DRAW_ARROW, STYLE_SOLID, 2);
   SetIndexArrow(0, 233);
   SetIndexEmptyValue(0, EMPTY_VALUE);

   SetIndexBuffer(1, OverboughtArrow);
   SetIndexStyle(1, DRAW_ARROW, STYLE_SOLID, 2);
   SetIndexArrow(1, 234);
   SetIndexEmptyValue(1, EMPTY_VALUE);

   IndicatorShortName("Williams %R Zone Entry Arrow");
   return(INIT_SUCCEEDED);
  }

//+------------------------------------------------------------------+
//| Custom indicator iteration function                               |
//+------------------------------------------------------------------+
int OnCalculate(const int rates_total,
                const int prev_calculated,
                const datetime &time[],
                const double &open[],
                const double &high[],
                const double &low[],
                const double &close[],
                const long &tick_volume[],
                const long &volume[],
                const int &spread[])
  {
   int needed = InpPeriod + 2;
   if(rates_total < needed)
      return(0);

   int limit = (prev_calculated == 0) ? rates_total - 2
                                       : rates_total - prev_calculated + 1;
   if(limit > rates_total - 2)
      limit = rates_total - 2;

   for(int i = limit; i >= 0; i--)
     {
      OversoldArrow[i]   = EMPTY_VALUE;
      OverboughtArrow[i] = EMPTY_VALUE;

      double wpr0 = iWPR(NULL, 0, InpPeriod, i);
      double wpr1 = iWPR(NULL, 0, InpPeriod, i + 1);

      if(wpr0 <= InpOversold && wpr1 > InpOversold)
         OversoldArrow[i] = wpr0 - InpArrowGapPoints;
      else if(wpr0 >= InpOverbought && wpr1 < InpOverbought)
         OverboughtArrow[i] = wpr0 + InpArrowGapPoints;
     }

   return(rates_total);
  }
//+------------------------------------------------------------------+