MATLAB FINANCIAL DERIVATIVES TOOLBOX Manual do Utilizador descarregar pdf (Página 43)

position (2,1) is taken to be the second (2), the (3,1) the third and finally the

(m, n) element is the last one (n*m). View the following example to

understand this king of matrix indexing.

Matlab’s command:

>> H=magic(4), H(1), H(2), H(9), H(16)

Matlab’s response:

H =

16 2 3 13

5 11 10 8

9 7 6 12

4 14 15 1

ans =

Comments:

Extracting specific elements from a matrix using single indexing.

For matrices, the colon notation “:” plays an important role. Colon can be

used to extract either a specific part of a matrix, or to view a whole row, a

whole column or a sub-matrix extracted from the original one. Earlier, the

colon was used to define vectors and it has been explained that it creates

elements from a starting_value through a finishing_value equally spaced

according to a defined step (if the step is not defined, then the step is taken

to be 1). In Matlab, a certain row of a matrix can be extracted by placing the

colon in the row_index, “K(:,column_index)”, and a certain column by placing

the colon in the column_index, “K(row_index:,:)”. A sub-matrix that is

composed by the r1 to r2 rows (r1=r2) and c1 to c2 columns (c1=c2) of the

original matrix can be retrieved according to the following syntax:

“K(r1:r2, c1:c2)”

1 2 ... 38 39 40 41 42 43 44 45 46 47 48 ... 118 119

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MATLAB FINANCIAL DERIVATIVES TOOLBOX Manual do Utilizador Página 43