Problem with arrays out of range

[Caio Araújo]

Hello guys, I'm new with MQL5 and I am trying to create a indicator which calculates the standard deviation from a vector of new calculated prices of the diference between close and opening from each candle.

I have successfully created the moving average with no problem but when I use MA values to calculate the STD there is no error running the code, but there is a error of array out of range in the expert tab.

can anyone just point what is wrong with my code? 

int OnInit()
  {
//--- indicator buffers mapping
   SetIndexBuffer(0,std_COBuffer,INDICATOR_DATA);
   SetIndexBuffer(0,ma_coBuffer,INDICATOR_CALCULATIONS);
   SetIndexBuffer(1,C_OBuffer,INDICATOR_CALCULATIONS);
   
//---
   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[])
  {
//---
   for(int i=0;i<rates_total;i++)
     {
        
      C_OBuffer[i] = close[i]-open[i];
      if(i>periodo)
        {
          ma_coBuffer[i]=SimpleMA(i,periodo,C_OBuffer); // OK works normal.
        }
        
      }
      
    for(int i=0;i<rates_total;i++)
      {
         if(i>=periodo)
             {
                std_COBuffer[i] = StdDev_Func(i,C_OBuffer,ma_coBuffer,periodo); //array out of range??
             }
       }          
    
//--- return value of prev_calculated for next call
   return(rates_total);
  }
//+------------------------------------------------------------------+
double StdDev_Func(const int position,const double &price[],const double &ma_price[],const int period)
  {
   double std_dev=0.0;
//--- calcualte StdDev
   if(position>=period)
     {
      for(int i=0; i<period; i++)
         std_dev+=MathPow(price[position-i]-ma_price[position],2.0);
      std_dev=MathSqrt(std_dev/(period-1));
     }
//--- return calculated value
   return(std_dev);
  }

[Dominik Egert]

Whatever position has for a value, you are subtracting i from it, this will and must lead to a value below NULL... That's why you are out of range.

EDIT: the debugger would have shown you...

[Caio Araújo]

Dominik Egert:

Whatever position has for a value, you are subtracting i from it, this will and must lead to a value below NULL... That's why you are out of range.

EDIT: the debugger would have shown you...

yep, thats it. thank you very much

[Mahadi Hasan Razu]

For the beginners it's very common problem. If you understand it's very easy to solve. Suppose an array size is 10 i.e. array[10] that it's index start from 0 to 9. Somehow inside code if there something happened that index become less than 0 or more than 9 then this array out of range happen.