Hi there,

I am new to Quantopian and want to try out a basic Bollinger method based on 1 minute candles. I want to by when below lower bb and sell as soon as the middle band gets crossed with the limitation that the sell should only happen if its profitable.

thats the current code based on a example code from Quantopian:

import quantopian.algorithm as algo  
from quantopian.pipeline import Pipeline  
from quantopian.pipeline.data.builtin import USEquityPricing  
from quantopian.pipeline.filters import Q1500US


import talib  
import numpy as np  
import pandas as pd

# Setup our variables  
def initialize(context):  
    context.exitafterlossof = True  
    context.losspcent = 0.97  
    context.stock = symbol('AAPL')  
    set_benchmark(symbol('AAPL'))  
    set_commission(commission.PerTrade(cost=20.00))

def handle_data(context, data):

    current_position = context.portfolio.positions[context.stock].amount  
    price=data[context.stock].price  
    costBasis = context.portfolio.positions[context.stock].cost_basis  
    # Load historical data for the stocks  
    prices = history(15, '1m', 'price')

    upper, middle, lower = talib.BBANDS(  
        prices[context.stock],  
        timeperiod=10,  
        # number of non-biased standard deviations from the mean  
        nbdevup=2,  
        nbdevdn=1,  
        # Moving average type: simple moving average here  
        matype=0)  
    # If price is below the recent lower band and we have  
    # no long positions then invest the entire  
    # portfolio value into SPY  
    if price <= lower[-1] and current_position <= 0:  
        order_target_percent(context.stock, 1.0)  
        print "buyprice"  
        print price  
    # If price is above the recent middle band and higher than buying price was  
    # exit position  
    elif price >= middle[-1] and current_position >= 0 and price > costBasis:  
        #and buyprice > current_price:  
        order_target_percent(context.stock, 0.0)  
        print "sellprice"  
        print price  
    record(upper=upper[-1],  
           lower=lower[-1],  
           mean=middle[-1],  
           price=price,  
           position_size=current_position)  

from what I understand the "price > costBasis:" should do what I want but the backtesting tells me that I am selling at loss, why??

Any help is appreciated.

Thx

Thorsten