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# floorbybk

Price floor instrument from Black-Karasinski interest-rate tree

## Syntax

```[Price, PriceTree] = floorbybk(BKTree, Strike, Settle, Maturity,Reset, Basis, Principal, Options)
```

## Arguments

 BKTree Interest-rate tree structure created by bktree. Strike Number of instruments (NINST)-by-1 vector of rates at which the floor is exercised. Settle Settlement date. NINST-by-1 vector of dates representing the settlement dates of the floor. The Settle date for every floor is set to the ValuationDate of the BK tree. The floor argument Settle is ignored. Maturity NINST-by-1 vector of dates representing the maturity dates of the floor. Reset (Optional) NINST-by-1 vector representing the frequency of payments per year. Default = 1. Basis (Optional) Day-count basis of the instrument. A vector of integers.0 = actual/actual (default)1 = 30/360 (SIA)2 = actual/3603 = actual/3654 = 30/360 (BMA)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/actual (ISDA)13 = BUS/252For more information, see basis. Principal (Optional) The notional principal amount. Default = 100. Options (Optional) Derivatives pricing options structure created with derivset.

## Description

[Price, PriceTree] = floorbybk(BKTree, Strike, Settlement, Maturity, Reset, Basis, Principal, Options) computes the price of a floor instrument from a Black-Karasinski tree.

Price is an NINST-by-1 vector of the expected prices of the floor at time 0.

PriceTree is the tree structure with values of the floor at each node.

## Examples

Price a 3% floor 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 floor instrument.

```load deriv.mat;
```

Set the required values. Other arguments will use defaults.

```Strike = 0.03;
Settle = '01-Jan-2005';
Maturity = '01-Jan-2009';
```

Use floorbyhw to compute the price of the floor instrument.

`Price = floorbybk(BKTree, Strike, Settle, Maturity)`
```Price =

0.2061
```