Re: [Quantlib-users] Error with PiecewiseConvexMonotoneZero

[Peter C. <pca...@gm...>]

Hi,

what I meant is that we should export

export_piecewise_curve(PiecewiseConvexMonotoneForward,ForwardRate,ConvexMonotone);

instead of "PiecewiseConvexMonotoneZero" and use that.

I am not sure if that explains your issues, since I never tried to use
convex monotone interpolation with the zero yield as the interpolation
variable.

Thank you
Peter

On Tue, 26 Dec 2023 at 21:46, Quant <qua...@gm...> wrote:
>
> Hi Peter,
>
> Thanks for the feedback. The workaround you suggested of avoiding the extrapolation of the curve worked and also removing the "Forward Rate" in the node_data as the forward rate is not exported in SWIG as you indicated. I think it will be helpful if the forward rates can be exported in SWIG as well on the next updates.
>
> I did 2 plots for the PiecewiseLogCubicDiscount and the PiecewiseConvexMonotoneZero for both zero and forward rates curves (tried to attach the plots but the email became too large i.e., more than 100KB to be posted). The PiecewiseConvexMonotoneZero is not smooth (quite weird curve) and I was wondering if the one implemented in QuantLib is the "Monotone convex (unameliorated)" described in the Hagan and West Paper as the best interpolation method? Is it perhaps possible to add the smoothed version of the interpolation on the upcoming updates? Please note that the plots below are related to the bootstrapping of government bonds.
>
> On a separate note, I tried using PiecewiseConvexMonotoneZero on deposits + FRA + Swap Rates bootstrapping and I got the following error;
>
> Traceback (most recent call last):
>   File "/Users/Library/CloudStorage/OneDrive-Personal/QuantLib Software/Valuations/Valuation of ZAR IRS/ZAR IRS Valuation 2.py", line 115, in <module>
>     zero_rate = curve.zeroRate(date, day_count, ql.Annual).rate()
>   File "/usr/local/lib/python3.9/site-packages/QuantLib/QuantLib.py", line 8610, in zeroRate
>     return _QuantLib.YieldTermStructure_zeroRate(self, *args)
> RuntimeError: 1st iteration: failed at 13th alive instrument, pillar May 28th, 2020, maturity May 28th, 2020, reference date February 28th, 2019: root not bracketed: f[-1,1] -> [-1.339261e-01,-1.181714e+01]
>
>
> What could be the cause of the error on this one?
>
> Thanks and regards,
>
> On Mon, Dec 25, 2023 at 8:17 PM Peter Caspers <pca...@gm...> wrote:
>>
>> Hi, the error is probably generated here
>>
>> https://github.com/lballabio/QuantLib/blob/master/ql/termstructures/yield/zerocurve.hpp#L168
>>
>> so a workaround would be to avoid extrapolating the curve.
>>
>> In fact I think the convex monotone interpolation was designed to be
>> applied to forward rates rather than zero yields, see
>>
>> https://downloads.dxfeed.com/specifications/dxLibOptions/HaganWest.pdf
>>
>> in section 6. But it seems only zero yield is exported as an
>> interpolation variable in SWIG at the moment
>>
>> https://github.com/lballabio/QuantLib-SWIG/blob/master/SWIG/piecewiseyieldcurve.i#L168
>>
>> We should add forward rate here I guess?
>>
>> Best
>> Peter
>>
>> On Sun, 24 Dec 2023 at 15:18, Quant <qua...@gm...> wrote:
>> >
>> > Hi QuantLib Users,
>> >
>> > I am trying to implement the Convex Monotone interpolation as shown below;
>> >
>> > curve = ql.PiecewiseConvexMonotoneZero(today, helpers, day_count)
>> > # curve = ql.PiecewiseLogMixedLinearCubicDiscount(today, helpers, day_count)
>> > # curve = ql.PiecewiseSplineCubicDiscount(today, helpers, day_count)
>> >
>> > # Enable Extrapolation:
>> > # This line enables extrapolation for the yield curve.
>> > # Extrapolation allows the curve to provide interest rates or rates beyond the observed data points,
>> > # which can be useful for pricing or risk management purposes.
>> > curve.enableExtrapolation()
>> >
>> > # Print the Zero Rates, Forward Rates and Discount Factors at node dates
>> > # print(pd.DataFrame(curve.nodes()))
>> > node_data = {'Date': [],
>> >              'Zero Rates': [],
>> >              'Forward Rates': [],
>> >              'Discount Factors': []}
>> >
>> > for dt in curve.dates():
>> >     node_data['Date'].append(dt)
>> >     node_data['Zero Rates'].append(curve.zeroRate(dt, day_count, ql.Compounded, ql.Annual).rate())
>> >     node_data['Forward Rates'].append(curve.forwardRate(dt, dt + ql.Period(1, ql.Years), day_count, ql.Annual).rate())
>> >     node_data['Discount Factors'].append(curve.discount(dt))
>> >
>> > node_dataframe = pd.DataFrame(node_data)
>> >
>> > And I am getting the following error;
>> >
>> > Traceback (most recent call last):
>> >   File "/Users/Library/CloudStorage/OneDrive-Personal/QuantLib Software/Valuations/IRS using Bond Bootstrapping/IRS using Bond Bootstrapping 3.py", line 87, in <module>
>> >     node_data['Forward Rates'].append(curve.forwardRate(dt, dt + ql.Period(1, ql.Years), day_count, ql.Annual).rate())
>> >   File "/usr/local/lib/python3.9/site-packages/QuantLib/QuantLib.py", line 8617, in forwardRate
>> >     return _QuantLib.YieldTermStructure_forwardRate(self, *args)
>> > RuntimeError: Convex-monotone spline derivative not implemented
>> >
>> > Is this a known issue with PiecewiseConvexMonotoneZero or it's an error that can be fixed in my code? If it can be fixed where do I need to fix?
>> >
>> > Thanks & regards,
>> > _______________________________________________
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