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My algorithm won't sell shares, only buy. Check my code?

My code seems to buy when there is a signal, however, when the signal is under 0 my program does not sell. Essentially my algorithm buys and buys and buys putting my paper trading bank account into debt... Please Help here is my code:

import math  
# model parameters  
price_scale = 150  
k = 2*math.pi/price_scale  
phase = 2*math.pi*0  
amplitude = 1

def initialize(context):  
    context.stock = sid(30160)  
    context.max_notional = 1000000.1  
    context.min_notional = 0

# Will be called on every trade event for the securities you specify.  
def handle_data(context, data):  
    close_p = data[context.stock].close_price  
    low_p = data[context.stock].low  
    signal = amplitude*math.cos(k*(close_p+low_p)+phase)  
    # plot a time series of the signal  
    notional = context.portfolio.positions[context.stock].amount * close_p  
    if signal >= 0 and notional < context.max_notional:  
        # buy  
        order(context.stock, 100)  
    elif notional > context.min_notional:  
        # sell  
        order(context.stock, -100)  
1 response

There are sell orders being issued. You can see this in the Transaction Details of the results. The reason you are seeing many more buy orders is because of the if else condition. It appears the first if statement evaluates true most of the time so the second one is reached less frequently.