def yield_in(transaction_file):
df = read_file(transaction_file)
dates = sorted(pd.unique(df.dt_date.ravel()).tolist())
dates.append(date.today())
for i, d in enumerate(dates):
if i != len(dates) - 1:
d2 = dates[i + 1] - timedelta(days=2)
startprice = worth_at_date(transaction_file, d).sum()
endprice = worth_at_date(transaction_file, d2).sum()
print cv.get_yield(d, startprice, d2, endprice)
print startprice
print endprice