MATLAB FINANCIAL DERIVATIVES TOOLBOX Uživatelský manuál stáhnout pdf (Strana 69)

Fourth Section

4. Control Flow

A collection of commands that include repetition of a conditional code

segment is termed as control flow structure. In Matlab as in any

programming language, control flow commands are presented via the

execution of a conditional expression (e.g. execute a code segment if a

statement is true) that is based on logical and/or relational operators.

4.1. Logical and Relational Operators

To evaluate a conditional code, it is needed to have a Boolean expression

that takes two possible values: TRUE or FALSE. Matlab defines a TRUE

statement with the value of 1 and a FALSE with the value of 0. In Matlab

there are six relational operators: “<” (less than), “<=” (less than or equal to),

“>” (greater than), “>=” (greater than or equal to), “==” (equal to), and “~=”

(not equal to). These can be used to compare a variable to a scalar, a vector

to a vector or a multidimensional array to another one. Always the

comparisons are done element by element and the result is a

scalar/vector/matrix of the same size as then ones originally used, with

elements set to one where the relation is true and elements set to zero where

it is not.

In addition, Matlab has (at least) 3 logical operators: “&” (logical AND), “|”

(logical OR), and “~” {logical complement - not). If we have two matrices “A”

and “B” that share the same dimensionality then:

• “A” & “B” is a matrix whose elements are 1's where both “A” and “B”

have non-zero elements, and 0's where either has a zero element. “A”

and “B” must have the same dimensions (or one can be a scalar). For

example in the case of scalars: 1 & 0, 0 & 1 and 0 & 0 will result to 0

(FALSE) while 1 & 1 is 1 (TRUE).

• “A” | “B” is a matrix whose elements are 1's where both “A” or “B” has

a non-zero element and 0's where both have zero elements. “A” and

“B” must have the same dimensions (or one can be a scalar). For

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MATLAB FINANCIAL DERIVATIVES TOOLBOX Uživatelský manuál Strana 69