My Buffer plotted, while not assigned.

[Jefferson Judge Metha]

Good day.for years now I have always had a question. 

Say you make an indicator with 4 buffers and 4 plots. 

All are set to array series true  

And wen you compile without assigning any values to the buffers, they will be ploted

[Yashar Seyyedin]

A plot has to be plotted unless it is of DRAW_NONE type.

[Tobias Johannes Zimmer]

https://www.mql5.com/en/docs/customind/setindexbuffer

It says SetIndexBuffer has INDICATOR _DATA as default value..

[Jefferson Judge Metha]

//+------------------------------------------------------------------+
//|                                                  Default Bug.mq5 |
//|                                                  Jefferson Metha |
//|                                             https://www.mql5.com |
//+------------------------------------------------------------------+
#property copyright "Jefferson Metha"
#property link      "https://www.mql5.com"
#property version   "1.00"
#property indicator_chart_window
#property indicator_buffers 3
#property indicator_plots   3
//--- plot Label1
#property indicator_label1  "Label1"
#property indicator_type1   DRAW_LINE
#property indicator_color1  clrRed
#property indicator_style1  STYLE_SOLID
#property indicator_width1  1
//--- plot Label2
#property indicator_label2  "Label2"
#property indicator_type2   DRAW_HISTOGRAM
#property indicator_color2  clrRed
#property indicator_style2  STYLE_SOLID
#property indicator_width2  1
//--- plot Label3
#property indicator_label3  "Label3"
#property indicator_type3   DRAW_ARROW
#property indicator_color3  clrRed
#property indicator_style3  STYLE_SOLID
#property indicator_width3  1
//--- input parameters
input int      Input1;
//--- indicator buffers
double         Label1Buffer[];
double         Label2Buffer[];
double         Label3Buffer[];
//---
int handle1=INVALID_HANDLE;
//+------------------------------------------------------------------+
//| Custom indicator initialization function                         |
//+------------------------------------------------------------------+
int OnInit()
  {
//--- indicator buffers mapping
   SetIndexBuffer(0,Label1Buffer,INDICATOR_DATA);
   SetIndexBuffer(1,Label2Buffer,INDICATOR_DATA);
   SetIndexBuffer(2,Label3Buffer,INDICATOR_DATA);
//--- setting a code from the Wingdings charset as the property of PLOT_ARROW
   PlotIndexSetInteger(2,PLOT_ARROW,159);
   //---
   ArraySetAsSeries(Label1Buffer,true);
   ArraySetAsSeries(Label2Buffer,true);
   ArraySetAsSeries(Label3Buffer,true);
   //---
   handle1=iMA(NULL,PERIOD_CURRENT,12,0,MODE_EMA,PRICE_CLOSE);
//---
   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[])
  {
//---
CopyBuffer(handle1,0,0,rates_total,Label1Buffer);
   
//--- return value of prev_calculated for next call
   return(rates_total);
  }
//+------------------------------------------------------------------+
//| Timer function                                                   |
//+------------------------------------------------------------------+
void OnTimer()
  {
//---
   
  }
//+------------------------------------------------------------------+
//| ChartEvent function                                              |
//+------------------------------------------------------------------+
void OnChartEvent(const int id,
                  const long &lparam,
                  const double &dparam,
                  const string &sparam)
  {
//---
   
  }
//+------------------------------------------------------------------+

The Above Code has a bug, as the unassigned Buffers have values to Them. 

[Conor Mcnamara]

for some drawing styles you may need to initialize buffers to an empty value as part of the initialization

 PlotIndexSetDouble(0,PLOT_EMPTY_VALUE,0.0);
 PlotIndexSetDouble(1,PLOT_EMPTY_VALUE,0.0);
 PlotIndexSetDouble(2,PLOT_EMPTY_VALUE,0.0);

they have it in the example code:

https://www.mql5.com/en/docs/constants/indicatorconstants/customindicatorproperties

but it's not really explained