Two colors in an indicator with one buffer possible?

[Marbo]

Hey guys,

I made a small indicator which shows inside candles. Now I want to check if the candle's close is above or below the open price and I want to change the color of the dot accordingly.

I know how to do this with two buffers but I want to know if it's possible with one buffer and how I could change the color of the buffer depending on the candle's close?

#property indicator_chart_window
#property indicator_buffers   1
#property indicator_plots     1

#property indicator_type1   DRAW_ARROW 
#property indicator_color1  clrYellow 
#property indicator_width1  1 

double buffer[];

//+------------------------------------------------------------------+
//| Custom indicator initialization function                         |
//+------------------------------------------------------------------+
void OnInit() {
   IndicatorSetInteger(INDICATOR_DIGITS,_Digits);  
   SetIndexBuffer(0,buffer,INDICATOR_DATA); 
   PlotIndexSetInteger(0,PLOT_ARROW,159); 
   PlotIndexSetDouble(0,PLOT_EMPTY_VALUE,EMPTY_VALUE); 
}
//+------------------------------------------------------------------+
//| 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[]) {
                
   if (rates_total<3) return (0);
   int start;
   if (prev_calculated<5) {
      start=2;
      ArrayInitialize(buffer,EMPTY_VALUE);
   }
   else start=rates_total-1;
   for (int i=start;i<rates_total-1 && !IsStopped();i++) {
      if ((high[i]<high[i-1] && low[i]>low[i-1])) {
         buffer[i]=(high[i]+low[i])/2;
      }
      else buffer[i]=EMPTY_VALUE;
   }
   return (rates_total);
}
//+------------------------------------------------------------------+

[Yashar Seyyedin]

https://www.mql5.com/en/docs/customind/indicators_examples/draw_color_arrow

[Conor Mcnamara]

 I was going to post this link as well ^

note, from the reference:

The number of buffers required for plotting DRAW_COLOR_ARROW is 2.

• a buffer to store the value of the price which is used to draw the symbol (plus a shift in pixels, given in the PLOT_ARROW_SHIFT property);
• a buffer to store the color index, which is used to draw an arrow (it makes sense to set only non-empty values).

Change your start index so that it removes unnecessary processing overhead

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[]) {
                
   if (rates_total<3) return (0);

   if (prev_calculated<5) {
      ArrayInitialize(buffer,EMPTY_VALUE);
   }

   int start = (prev_calculated == 0) ? 1 : prev_calculated - 1;
   
   for (int i=start;i<rates_total-1 && !IsStopped();i++) {
      if ((high[i]<high[i-1] && low[i]>low[i-1])) {
         buffer[i]=(high[i]+low[i])/2;
      }
      else buffer[i]=EMPTY_VALUE;
   }
   return (rates_total);
}

[Fernando Carreiro]

Your topic has been moved to the section: Technical Indicators
Please consider which section is most appropriate — https://www.mql5.com/en/forum/172166/page6#comment_49114893

[Marbo]

Got it. Thanks guys!