Modeling Amortizing Swaps and Previously Fixed Floating Coupons

# Quantlib: Interest rate swap starting before valuation date


# Quantlib: Interest rate swap starting before valuation date












I am trying to evaluate an interest rate swap starting before the valuation date with an amortizing schedule(in Python). I am using your (i.e. Quantilb) codes but i can't figure out how to solve my problem. I am following this example http://gouthamanbalaraman.com/blog/interest-rate-swap-quantlib-python.html. The first problem is that i have nominal amount decreasing with ammortization schedule. The second, I have an evaluation date following the first reference date. So I have the first coupon of the floating rate leg already defined and I need to discount its crashflow in the swap

Thanks in advance

```
from QuantLib import *

import matplotlib.pyplot as plt
import numpy 
from cookielib import MONTHS

today = Date(1,1,2017)
Settings.instance().evaluationDate = today

from matplotlib.ticker import FuncFormatter
from utils import *

def format_rate(r):
    return '{0:.4f}'.format(r.rate()*100.00)

def plot_curves(*curves):
    fig, ax = plt.subplots()
    ax.set_xticks([0,5,10,15,20,25,30,35,40,45,50,55,60,65,100])

    times = numpy.linspace(0, 61, 4000)
    for curve, style in curves:
        rates = [ curve.zeroRate(t, Continuous).rate() for t in times ]
        plt.plot(times, rates, style)
        #print zip(times, rates)

    #print curve.zeroRate(1, Continuous).rate()    
    plt.show()

def plot_curve(curve):
    plot_curves((curve,'-'))

quotes = [SimpleQuote(-0.00373), SimpleQuote(-0.00329), SimpleQuote(-0.00271)]
helpers = [SwapRateHelper(QuoteHandle(quotes[0]),Period(1, Months), TARGET(),Months, Preceding,  Actual360(),Euribor1M())]
helpers.append(SwapRateHelper(QuoteHandle(quotes[1]),Period(3, Months), TARGET(),Months, Preceding,  Actual360(),Euribor3M()))
helpers.append(SwapRateHelper(QuoteHandle(quotes[2]),Period(6, Months), TARGET(),Months, Preceding,  Actual360(),Euribor6M()))

for rate, tenor in [(-0.00252, 1), (-0.00187, 2), (-0.00096, 3), (0.0001, 4), (0.00127, 5), (0.00247, 6), (0.00369, 7), (0.00505, 8), (0.00623, 9), (0.00732, 10), (0.00917, 12), (0.01116, 15), (0.01286, 20), (0.01349, 25), (0.01373, 30), (0.01378, 40), (0.01331, 50), (0.013, 61)]:
    quotes.append(SimpleQuote(rate))
    helpers.append(SwapRateHelper(QuoteHandle(quotes[-1]),Period(tenor, Years), TARGET(),Annual, Preceding,  Actual360(),Euribor1Y()))

rate_curve = PiecewiseLinearZero(0, TARGET(), helpers, Actual360())
print 'reference'
print rate_curve.referenceDate()

print '-------rate_curve.dates---------------'

for i, d in enumerate(rate_curve.dates()):
    print i+1, d, d.weekday()

curve_handle = RelinkableYieldTermStructureHandle(rate_curve)

fixed_schedule = Schedule(Date(22, 6, 2017), Date(22, 6, 2020),Period(6, Months), TARGET(), Preceding, Preceding, DateGeneration.Forward, False)
floating_schedule = Schedule(Date(22, 6, 2017), Date(22, 6, 2020),Period(6, Months), TARGET(), Preceding, Preceding, DateGeneration.Forward, False)

print '----------fixed_schedule----------------'

for i, d in enumerate(fixed_schedule):
    print i+1, d

print '----------floating_schedule-------------' 

for i, d in enumerate(floating_schedule):
    print i+1, d

index = Euribor1Y(curve_handle)

discountTermStructure = RelinkableYieldTermStructureHandle()

swap = VanillaSwap(VanillaSwap.Receiver,1000000, fixed_schedule, 0.2, Actual360(), floating_schedule, index, 0.185, Actual360())

swap_engine = DiscountingSwapEngine(curve_handle)
swap.setPricingEngine(swap_engine)

print '-----leg 0 ----------------------'

for i, cf in enumerate(swap.leg(0)):
    print "%2d    %-18s  %10.4f"%(i+1, cf.date(), cf.amount())

print '-----leg 1 ----------------------'

for i, cf in enumerate(swap.leg(1)):
    print "%2d    %-18s  %10.4f"%(i+1, cf.date(), cf.amount())

swap.setPricingEngine(DiscountingSwapEngine(curve_handle))
P0 = swap.NPV()

print '----floatingLegNPV-----'
print swap.floatingLegNPV()
print '----fixedLegNPV-----'
print swap.fixedLegNPV()
print '----NPV-----'
print P0

plot_curve(rate_curve)
```

Best regards Matteo

## Answer by Luigi Ballabio (score 0)

https://quant.stackexchange.com/a/35334

For the first problem: `VanillaSwap` doesn't allow amortization. You'll have to create the fixed and floating legs with `FixedRateLeg` and `IborLeg` (which take a list of notionals) and use them to build an instance of the `Swap` class.

For the second, if the rate of the floating cashflow has been fixed on date `d` to a rate `r`, you can run

```
index.addFixing(d, r);
```

to store the information and make it available for calculation.