//+------------------------------------------------------------------+
//|                                                        EMA计算.mq4 |
//|                                          Copyright 2023, 100w123 |
//|                                              https://100w123.com |
//+------------------------------------------------------------------+
#property copyright "Copyright 2023, 100w123"
#property link      "https://100w123.com"
#property version   "1.00"
#property strict
#property indicator_chart_window

#property indicator_buffers 2
#property indicator_color1 clrRed
#property indicator_width1 2
#property indicator_color2 clrYellow
#property indicator_width2 2

extern int  SMA_Period  = 10;
extern int  EMA_Period  = 20;

double buf[];
double ema[];

//+------------------------------------------------------------------+
int OnInit() {

    SetIndexBuffer(0, buf);
    SetIndexStyle(0, DRAW_LINE);
    SetIndexBuffer(1, ema);
    SetIndexStyle(1, DRAW_LINE);

    return(INIT_SUCCEEDED);
}

//+------------------------------------------------------------------+
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 i, j;
    int limit;
    if (prev_calculated == 0)
        limit = rates_total - 1;
    else
        limit = rates_total - prev_calculated;

    for (i = limit; i >= 0; i--) {
        // SMA
        if (i + SMA_Period - 1 <= Bars - 1) {

            buf[i] = 0;

            for (j = 0; j < SMA_Period; j++) buf[i] += Close[i + j];

            buf[i] /= SMA_Period;
        }

        /*
        // 一般的EMA
        if (i + EMA_Period - 1 <= Bars - 1)
        {
           if(i + EMA_Period - 1 == Bars - 1)
           {
              ema[i] = 0;
              for (j=0; j<EMA_Period; j++) ema[i] += Close[i+j];
              ema[i] /= EMA_Period;
           }
           else
           {
              ema[i] = ema[i+1] * (EMA_Period - 1) + Close[i] * 2;
              ema[i] /= EMA_Period + 1;
           }
        }
        */

        // MT4的EMA
        if (i == Bars - 1) ema[i] = Close[i];
        else {
            ema[i] = ema[i + 1] * (EMA_Period - 1) + Close[i] * 2;
            ema[i] /= EMA_Period + 1;
        }
    }

    return(rates_total);
}