Standard Deviation calculation in MT4

//+------------------------------------------------------------------+
//|                                       Meta COT Net Positions.mq4 |
//|   Copyright © 2009, C-4 (Vasiliy Sokolov, Russia, St.-Petersburg,|
//|                                      2009), All Rights Reserved. |
//|                                                   [email protected] |
//+------------------------------------------------------------------+
// Ïîêàçûâàåò ÷èñòûå ïîçèöèè òðåéäåðîâ.
//see also: "Meta COT Project - New Horizons for CFTC Report Analysis in MetaTrader 4", http://articles.mql4.com/867
#property copyright "Copyright © 2009, C-4 (Vasiliy Sokolov ([email protected]), SPb), All Rights Reserved. // mod. fxdaytrader"
#property link      "http://ForexBaron.net"
#property indicator_separate_window
#property  indicator_buffers 12
#property  indicator_color1  Green
#property  indicator_color2  Blue
#property  indicator_color3  Red
#property  indicator_color4  Silver
#property  indicator_color5  Green
#property  indicator_color6  Blue
#property  indicator_color7  Red
#property  indicator_color8  Silver
#property  indicator_color9  Green
#property  indicator_color10  Blue
#property  indicator_color11  Red
#property  indicator_color12  Silver
   #property indicator_level1     0
int  period=52;
int movement_index=6;
extern int ma_period = 52;
input int sd_period = 1;
extern color ColorOpenInterest = Green;
extern color ColorNonComm = Blue;
extern color ColorOperators = Red;
extern color ColorNonRep = Silver;
extern bool Show_nNoncomm=true;//false;
extern bool Show_nOperators=false;//false;
extern bool Show_nNonrep=false;//false;
extern bool Show_nOI=false;
bool printerror=false;//fxdaytrader
double i_open_interest[];
double i_noncomm[];
double i_operators[];
double i_nonrep[];
double sd_oi[], sd_nc[], sd_cm[], sd_nr[], ma_oi[], sd_up_oi[], sd_lo_oi[], ma_nc[], sd_up_nc[], sd_lo_nc[], ma_cm[], sd_up_cm[], sd_lo_cm[], 
ma_nr[], sd_up_nr[], sd_lo_nr[], cavg_oi[], cavg_nc[], cavg_cm[], cavg_nr[],mid_oi[], mid_nc[], mid_cm[], mid_nr[];
#include <cotlib.mq4>
int init()
{
   if(init_data()==false)error=true;
   if(error==false)load_data();
   if(error==false)count_data();
   SetParam();
   return 0;
}
int start()
{
   
   if (error) if (!printerror) { printerror=true; Print("ERROR="+GetLastError()); } if (!error) printerror=false;
   DrowData();
   return 0;
}
void SetParam()
{
   SetIndexStyle(0,DRAW_LINE,STYLE_SOLID,1,ColorOpenInterest);
   SetIndexStyle(1,DRAW_LINE,STYLE_SOLID,1,ColorOpenInterest);
   SetIndexStyle(2,DRAW_LINE,STYLE_SOLID,1,ColorOpenInterest);
   SetIndexStyle(3,DRAW_LINE,STYLE_SOLID,1,ColorNonComm);
   SetIndexStyle(4,DRAW_LINE,STYLE_SOLID,1,ColorNonComm);
   SetIndexStyle(5,DRAW_LINE,STYLE_SOLID,1,ColorNonComm);
   SetIndexStyle(6,DRAW_LINE,STYLE_SOLID,1,ColorOperators);
   SetIndexStyle(7,DRAW_LINE,STYLE_SOLID,1,ColorOperators);
   SetIndexStyle(8,DRAW_LINE,STYLE_SOLID,1,ColorOperators);
   SetIndexStyle(9,DRAW_LINE,STYLE_SOLID,1,ColorNonRep);
   SetIndexStyle(10,DRAW_LINE,STYLE_SOLID,1,ColorNonRep);
   SetIndexStyle(11,DRAW_LINE,STYLE_SOLID,1,ColorNonRep);
   IndicatorDigits(0);
   SetIndexEmptyValue(0,0.0);
   SetIndexEmptyValue(1,0.0);
   SetIndexEmptyValue(2,0.0);
   SetIndexEmptyValue(3,0.0);
   SetIndexEmptyValue(4,0.0);
   SetIndexEmptyValue(5,0.0);
   SetIndexEmptyValue(6,0.0);
   SetIndexEmptyValue(7,0.0);
   SetIndexEmptyValue(8,0.0);
   SetIndexEmptyValue(9,0.0);
   SetIndexEmptyValue(10,0.0);
   SetIndexEmptyValue(11,0.0);
   
   if(load_cot_file==true)IndicatorShortName(StringConcatenate("Meta COT Net Pos SD.: ", str_trim(cot_file)));
   else IndicatorShortName(StringConcatenate("Meta COT Net Pos SD.: ", name));
   
   if(Show_nOI==true){
      SetIndexBuffer(0,sd_up_oi);
      SetIndexLabel(0, "Open Interest + "+sd_period+" SD");
      SetIndexBuffer(1,mid_oi);
      SetIndexLabel(1, "Open Interest Average");
      SetIndexBuffer(2,sd_lo_oi);
      SetIndexLabel(2, "Open Interest - "+sd_period+" SD");
   }
   if(Show_nNoncomm==true){
      SetIndexBuffer(3,sd_up_nc);
      SetIndexLabel(3, "Net Non Commercial + "+sd_period+" SD");
      SetIndexBuffer(4,mid_nc);
      SetIndexLabel(4, "Net Non Commercial Average");
      SetIndexBuffer(5,sd_lo_oi);
      SetIndexLabel(5, "Net Non Commercial - "+sd_period+" SD");
   }
   if(Show_nOperators==true){
      SetIndexBuffer(6,sd_up_cm);
      SetIndexLabel(6, "Net Commercial + "+sd_period+" SD");
      SetIndexBuffer(7,mid_cm);
      SetIndexLabel(7, "Net Commercial Average");
      SetIndexBuffer(8,sd_lo_cm);
      SetIndexLabel(8, "Net Commercial - "+sd_period+" SD");
   } 
   if(Show_nNonrep==true){
      SetIndexBuffer(9,sd_up_nr);
      SetIndexLabel(9, "Net Non Reportable + "+sd_period+" SD");
      SetIndexBuffer(10,mid_nr);
      SetIndexLabel(10, "Net Non Reportable Average");
      SetIndexBuffer(11,sd_lo_nr);
      SetIndexLabel(11, "Net Non Reportable - "+sd_period+" SD");
   }
}
void DrowData()
{
   int end_data=get_lastdata();
   for(int i=0;i<end_data;i++){
      i_open_interest[i]=get_data(OI, i);
      i_noncomm[i]=get_data(NET_NONCOMM, i);
      i_operators[i]=get_data(NET_OPERATORS, i);
      i_nonrep[i]=get_data(NET_NONREP,i);
      
      ma_oi[i] = iMAOnArray(i_open_interest,0,ma_period,0,MODE_SMA,i);
      ma_nc[i] = iMAOnArray(i_noncomm,0,ma_period,0,MODE_SMA,i);
      ma_cm[i] = iMAOnArray(i_operators,0,ma_period,0,MODE_SMA,i);
      ma_nr[i] = iMAOnArray(i_nonrep,0,ma_period,0,MODE_SMA,i);
      
      mid_oi[i] = ma_oi[i];
      sd_oi[i] =  iStdDevOnArray(i_open_interest,0,ma_period,0,MODE_SMA,i);
      sd_lo_oi[i] = mid_oi[i]-(sd_period*sd_oi[i]);
      sd_up_oi[i] = mid_oi[i]+(sd_period*sd_oi[i]);


      mid_nc[i] = ma_nc[i];
      sd_nc[i] =  iStdDevOnArray(i_noncomm,0,ma_period,0,MODE_SMA,i);
      sd_lo_nc[i] = mid_nc[i]-(sd_period*sd_nc[i]);
      sd_up_nc[i] = mid_nc[i]+(sd_period*sd_nc[i]);
      

      mid_cm[i] = ma_cm[i];
      sd_cm [i]=  iStdDevOnArray(i_operators,0,ma_period,0,MODE_SMA,i);
      sd_lo_cm[i] = mid_cm[i]-(sd_period*sd_cm[i]);
      sd_up_cm[i] = mid_cm[i]+(sd_period*sd_cm[i]);
      

      mid_nr[i] = ma_nr[i];
      sd_nr[i] =  iStdDevOnArray(i_nonrep,0,ma_period,0,MODE_SMA,i);
      sd_lo_nr[i] = mid_nr[i]-(sd_period*sd_nr[i]);
      sd_up_nr[i] = mid_nr[i]+(sd_period*sd_nr[i]);
   }
}