capbybk

Price cap instrument from Black-Karasinski interest-rate tree

Syntax

[Price,PriceTree] = capbybk(BKTree,Strike,Settle,Maturity)

[Price,PriceTree] = capbybk(___,CapReset,Basis,Principal,Options)

Description

[Price,PriceTree] = capbybk(BKTree,Strike,Settle,Maturity) computes the price of a cap instrument from a Black-Karasinski interest-rate tree. capbybk computes prices of vanilla caps and amortizing caps.

Note

Alternatively, you can use the Cap object to price cap instruments. For more information, see Get Started with Workflows Using Object-Based Framework for Pricing Financial Instruments.

[Price,PriceTree] = capbybk(___,CapReset,Basis,Principal,Options) adds optional arguments.

Examples

Price a 3% Cap Instrument Using a Black-Karasinski Interest-Rate Tree

Load the file deriv.mat, which provides BKTree. The BKTree structure contains the time and interest-rate information needed to price the cap instrument.

load deriv.mat;

Set the required values. Other arguments will use defaults.

Strike = 0.03;
Settle = datetime(2004,1,1);
Maturity = datetime(2007,1,1);

Use capbybk to compute the price of the cap instrument.

Price = capbybk(BKTree, Strike, Settle, Maturity)

Price = 
2.0965

Compute the Price of an Amortizing and Vanilla Caps Using the BK Model

Load deriv.mat to specify the BKTree and then define the cap instrument.

load deriv.mat; 
Settle = datetime(2004,1,1);
Maturity = datetime(2008,1,1);
Strike = 0.05;
CapReset = 1;
Principal ={{datetime(2005,1,1) 100;datetime(2006,1,1) 60;datetime(2007,1,1) 30;datetime(2008,1,1) 30};...
            100};

Price the amortizing and vanilla caps.

Basis = 1;
Price = capbybk(BKTree, Strike, Settle, Maturity, CapReset, Basis, Principal)

Price = 2×1

    0.2226
    0.7422

Input Arguments

BKTree — Interest-rate tree structure

structure

Interest-rate tree structure, specified by using bktree.

Data Types: struct

Strike — Rate at which cap is exercised

decimal

Rate at which cap is exercised, specified as a NINST-by-1 vector of decimal values.

Data Types: double

Settle — Settlement date for cap

datetime array | string array | date character vector

Settlement date for the cap, specified as a NINST-by-1 vector using a datetime array, string array, or date character vectors. The Settle date for every cap is set to the ValuationDate of the BK tree. The cap argument Settle is ignored.

To support existing code, capbybk also accepts serial date numbers as inputs, but they are not recommended.

Maturity — Maturity date for cap

datetime array | string array | date character vector

Maturity date for the cap, specified as a NINST-by-1 vector using a datetime array, string array, or date character vectors.

To support existing code, capbybk also accepts serial date numbers as inputs, but they are not recommended.

CapReset — Reset frequency payment per year

1 (default) | numeric

(Optional) Reset frequency payment per year, specified as a NINST-by-1 vector.

Data Types: double

Basis — Day-count basis of instrument

0 (actual/actual) (default) | integer from 0 to 13

(Optional) Day-count basis representing the basis used when annualizing the input forward rate, specified as a NINST-by-1 vector of integers.

• 0 = actual/actual

• 1 = 30/360 (SIA)

• 2 = actual/360

• 3 = actual/365

• 4 = 30/360 (PSA)

• 5 = 30/360 (ISDA)

• 6 = 30/360 (European)

• 7 = actual/365 (Japanese)

• 8 = actual/actual (ICMA)

• 9 = actual/360 (ICMA)

• 10 = actual/365 (ICMA)

• 11 = 30/360E (ICMA)

• 12 = actual/365 (ISDA)

• 13 = BUS/252

For more information, see Basis.

Data Types: double

Principal — Notional principal amount

100 (default) | numeric

(Optional) Notional principal amount, specified as a NINST-by-1 of notional principal amounts, or a NINST-by-1 cell array, where each element is a NumDates-by-2 cell array where the first column is dates and the second column is associated principal amount. The date indicates the last day that the principal value is valid.

Use Principal to pass a schedule to compute the price for an amortizing cap.

Data Types: double | cell

Options — Derivatives pricing options structure

structure

(Optional) Derivatives pricing options structure, specified using derivset.

Data Types: struct

Output Arguments

Price — Expected price of cap at time 0

vector

Expected price of the cap at time 0, returned as a NINST-by-1 vector.

PriceTree — Tree structure with values of cap at each node

vector

Tree structure with values of the cap at each node, returned as a MATLAB^® structure of trees containing vectors of instrument prices and a vector of observation times for each node:

• PriceTree.PTree contains cap prices.

• PriceTree.tObs contains the observation times.

• PriceTree.Connect contains the connectivity vectors. Each element in the cell array describes how nodes in that level connect to the next. For a given tree level, there are NumNodes elements in the vector, and they contain the index of the node at the next level that the middle branch connects to. Subtracting 1 from that value indicates where the up-branch connects to, and adding 1 indicated where the down branch connects to.

• PriceTree.Probs contains the probability arrays. Each element of the cell array contains the up, middle, and down transition probabilities for each node of the level.

More About

Cap

A cap is a contract that includes a guarantee that sets the maximum interest rate to be paid by the holder, based on an otherwise floating interest rate.

The payoff for a cap is:

$$\max (CurrentRate-CapRate,0)$$

For more information, see Cap.

Version History

Introduced before R2006a

R2022b: Serial date numbers not recommended

Although capbybk supports serial date numbers, datetime values are recommended instead. The datetime data type provides flexible date and time formats, storage out to nanosecond precision, and properties to account for time zones and daylight saving time.

To convert serial date numbers or text to datetime values, use the datetime function. For example:

t = datetime(738427.656845093,"ConvertFrom","datenum");
y = year(t)

y =

        2021

There are no plans to remove support for serial date number inputs.