Альфа эквивалентной EMA связана с длиной простой скользящей средней как            

Settings=
{
  Name = "ma_rsi_period2",
  period = 10,
  ID_RSI = "SBER_RSI_ID",
  line = 
       {
         { Name = "RSI MA Simple", 
      Color = #ff0000,
           Type = TYPE_LINE,
           Width = 2
         }
       }
}


function Init() 
   t = {}
   start_ind = 0 
   tindex = 0
   lastSMARSI = 0 
    return 1
end 

function OnCalculate(index)
   

   if index>=1 then
      Graph_RSI, Number_RSI, Legend_RSI = getCandlesByIndex(Settings.ID_RSI, 0, index-1, 1)
   else
      return nil
   end
   
   
   if Graph_RSI~=0 then
   
      local Graph_RSI = Graph_RSI[0].close
      
      if Graph_RSI == 0 or Graph_RSI == nil then 
         return nil 
      else
         if start_ind == 0 then start_ind = index end
      end
      
      
         if index < (Settings.period + start_ind) then
            
            if tindex < index then

               table.insert(t, Graph_RSI)
               tindex = index
            end
            
            
            return nil
                        
         else
            
            local sum = 0
            
            if index > tindex then
            
               table.insert(t, Graph_RSI)
               table.remove(t, 1)
               
               for i = 1, #t do
                  sum = sum + tonumber(t[i])
               end
               
               sum = sum + tonumber(Graph_RSI)
               tindex = index
            
               lastSMARSI = sum/Settings.period
               
               return sum/Settings.period
            
            
            end
         
            
            return lastSMARSI
         
         
         end
      
   else
      return nil
   end
   
end