ah, i shouldve put the results, sorry. I already found the fix :D

@ab_trader said in Sizer problem:

@Edward-Owen said in Sizer problem:

Some of the costs are negative.

cost = size x price
size is negative for short position, therfore cost is also negative.

I am quite new to python and backtrader, can you point me out which code is shorting my trades, I thought that my code only goes long.

thankss!

@ab_trader said in Sizer problem:

@Edward-Owen said in Sizer problem:

Some of the costs are negative.

cost = size x price
size is negative for short position, therfore cost is also negative.

I am quite new to python and backtrader, can you point me out which code is shorting my trades, I thought that my code only goes long.

@ab_trader okay that makes sense

So I tried using an example sizer from Backtest-Rookies and implemented it to my own code
https://backtest-rookies.com/2017/07/24/developing-sizers-backtrader-part-1/

#This is the example code that they provided:

class MaxRiskSizer(bt.Sizer):
    '''
    Returns the number of shares rounded down that can be purchased for the
    max rish tolerance
    '''
    params = (('risk', 0.03),)

    def __init__(self):
        if self.p.risk > 1 or self.p.risk < 0:
            raise ValueError('The risk parameter is a percentage which must be'
                'entered as a float. e.g. 0.5')

    def _getsizing(self, comminfo, cash, data, isbuy):
        if isbuy:
            size = math.floor((cash * self.p.risk) / data[0])
        else:
            size = math.floor((cash * self.p.risk) / data[0]) * -1
        return size

cerebro.addsizer(MaxRiskSizer, risk=0.5)

...............................................................................................................................................................
I set the risk at (risk = 0.5) , so it should mean I am going to use 50% of the portfolio to enter a trade right?

#This is my code(I seperated the stategy class and main):

1. Main:

import backtrader as bt
import datetime
import math
from Strategy import TestStrategy

cerebro = bt.Cerebro()
cerebro.broker.set_cash(100000)
cerebro.broker.setcommission(0.01)
data = bt.feeds.YahooFinanceCSVData(
    dataname="oracle.csv",
    fromdate=datetime.datetime(2000,3,1),
    todate=datetime.datetime(2000,4,29),
    reverse=False)
class MaxRiskSizer(bt.Sizer):
    '''
    Returns the number of shares rounded down that can be purchased for the
    max rish tolerance
    '''
    params = (('risk', 0.03),)

    def __init__(self):
        if self.p.risk > 1 or self.p.risk < 0:
            raise ValueError('The risk parameter is a percentage which must be'
                'entered as a float. e.g. 0.5')

    def _getsizing(self, comminfo, cash, data, isbuy):
        if isbuy:
            size = math.floor((cash * self.p.risk) / data[0])
        else:
            size = math.floor((cash * self.p.risk) / data[0]) * -1
        return size

cerebro.adddata(data)                   #Insert Data.
cerebro.addstrategy(TestStrategy)
#cerebro.addsizer(bt.sizers.FixedSize, stake=2)
cerebro.addsizer(MaxRiskSizer, risk=0.5)


print("Starting Portfolio :%.2f" % cerebro.broker.getvalue())
print()
cerebro.run()
print("Final Portfolio Value:%.2f" % cerebro.broker.getvalue())
cerebro.plot(style="candlestick",barup='green', bardown='red')

2. Strategy class :

import backtrader as bt

class TestStrategy(bt.Strategy):

    def log(self, txt, dt=None):
        ''' Logging function for this strategy'''
        dt = dt or self.datas[0].datetime.date(0)
        print('%s, %s' % (dt.isoformat(), txt))

    def __init__(self):
        # Keep a reference to the "close" line in the data[0] dataseries
        self.dataclose = self.datas[0].close
        # To keep track of pending orders and buy price/commission
        self.order = None
        self.buyprice = None
        self.buycomm = None

    def notify_order(self,order):
        if order.status in [order.Submitted, order.Accepted]:
            return

        # Check if an order has been completed. Broker could reject if not enough cash
        if order.status in[order.Completed]:
            if order.isbuy():
                self.log("BUY EXECUTED,Price: %.2f, Cost: %.2f, Comm %.2f" %
                         (order.executed.price,
                          order.executed.value,
                          order.executed.comm))

                self.buyprice = order.executed.price
                self.buycomm = order.executed.comm

            elif order.issell():
                self.log("SELL EXECUTED,Price: %.2f, Cost: %.2f, Comm %.2f" %
                         (order.executed.price,
                          order.executed.value,
                          order.executed.comm))

            self.bar_executed = len(self)

        elif order.status in [order.Canceled, order.Margin, order.Rejected]:
            self.log("Order Cancled/Margin/Rejected")

        self.order = None

    def notify_trade(self, trade):
        if not trade.isclosed:
            return

        self.log("OPERATION PROFIT, GROSS %.2f NET %.2f" %
                 (trade.pnl, trade.pnlcomm))
        print()

    def next(self):
        # Simply log the closing price of the series from the reference
        #self.log('Close, %.2f' % self.dataclose[0])

        if self.order:
            return

        #If we are not in the market, we might buy.
        if not self.position:
            if self.dataclose[0] < self.dataclose[-1]:
                # current close less than previous close

                if self.dataclose[-1] < self.dataclose[-2]:
                    # previous close less than the previous previous close

                    # BUY, BUY, BUY!!! (with all possible default parameters)
                    self.log('BUY CREATED, %.2f' % self.dataclose[0])
                    self.order = self.buy()
        else:
            if len(self) >= (self.bar_executed + 5):
                self.log("SELL CREATED {}".format(self.dataclose[0]))
                self.order = self.sell()

...............................................................................................................................................................
Starting Portfolio :100000.00

2000-03-02, BUY CREATED, 30.47
2000-03-03, BUY EXECUTED,Price: 31.63, Cost: 51873.20, Comm 518.73
2000-03-10, SELL CREATED 36.3
2000-03-13, SELL EXECUTED,Price: 34.91, Cost: 20717.65, Comm 228.66
2000-03-20, SELL CREATED 34.75
2000-03-21, SELL EXECUTED,Price: 34.63, Cost: 30289.80, Comm 349.76
2000-03-21, OPERATION PROFIT, GROSS 5103.40 NET 4014.90

2000-03-28, SELL CREATED 38.5
2000-03-29, SELL EXECUTED,Price: 38.28, Cost: -52099.08, Comm 520.99
2000-04-05, SELL CREATED 34.8
2000-04-06, SELL EXECUTED,Price: 35.86, Cost: -80577.42, Comm 805.77
2000-04-13, SELL CREATED 31.99
2000-04-14, SELL EXECUTED,Price: 31.10, Cost: -114821.20, Comm 1148.21
2000-04-24, SELL CREATED 32.22
2000-04-25, SELL EXECUTED,Price: 33.30, Cost: -180785.70, Comm 1807.86
Final Portfolio Value:75467.86
...............................................................................................................................................................

Problem is:

1. Just on the first buy, my portfolio starts at $100k but it uses $51.8k instead of amount < $50k. (Note: risk is 0.5)

2. Some of the costs are negative. :/

so,
how do I fix the negative, is there something I am missing out or don't understand?

ah, i shouldve put the results, sorry. I already found the fix :D

hi,

I am new to backtrader and even python. I know I shouldn't be rushing but I just wanna get this to work. I have only watched a few tutorials on backtrading but not much.

So I am planning to use the provided
https://www.backtrader.com/recipes/indicators/donchian/donchian/
and use it to execute a buy order on DC 5 day.

Here is the code
import backtrader as bt
import datetime

cerebro = bt.Cerebro()
cerebro.broker.set_cash(1000000)
data = bt.feeds.YahooFinanceCSVData(
dataname="oracle.csv",
fromdate=datetime.datetime(2000,1,1),
todate=datetime.datetime(2000,12,31),
reverse=False)

cerebro.adddata(data) #Insert Data.

class DonchianChannels(bt.Strategy):
#DONCHIAN CHANNELS PLOTTING
alias = ('DCH', 'DonchianChannel',)
lines = ( 'dch', 'dcl',) # dc middle, dc high, dc low
params = dict(
period=5,
lookback=-1, #look at Params Note.
)
plotinfo = dict(subplot=False) # plot along with data
plotlines = dict(
dch=dict(_samecolor=True), # use same color as prev line (dcm)
dcl=dict(_samecolor=True), # use same color as prev line (dch)
)

def __init__(self):
    self.dataclose = self.datas[0].close
    self.order = None
    #DC
    hi, lo = self.data.high, self.data.low
    if self.p.lookback:  # move backwards as needed
        hi, lo = hi(self.p.lookback), lo(self.p.lookback)
    self.l.dch = bt.ind.Highest(hi, period=self.p.period)
    self.l.dcl = bt.ind.Lowest(lo, period=self.p.period)
    self.l.dcm = (self.l.dch + self.l.dcl) / 2.0  # avg of the above
    
def next(self):
    # Simply log the closing price of the series from the reference
    self.log('Close, %.2f' % self.dataclose[0])

    if self.order:
        return

    if not self.position:
        if self.dataclose[-1] < self.l.dch:
            # previous close less than the previous previous close

            # BUY, BUY, BUY!!! (with all possible default parameters)
            self.log('BUY CREATE, %.2f' % self.dataclose[0])
            self.order = self.buy()
    else:
        if len(self) >= (self.bar_executed + 5):
            self.log("SELL CREATED {}".format(self.dataclose[0]))
            self.order = self.sell()

cerebro.addstrategy(DonchianChannels)

cerebro.addsizer(bt.sizers.FixedSize, stake=1000)
print("Starting Portfolio :%.2f" % cerebro.broker.getvalue())
cerebro.run()
print("Final Portfolio Value:%.2f" % cerebro.broker.getvalue())
cerebro.plot(style="candlestick",barup='green', bardown='red')