Graphics Programs Reference

In-Depth Information

We can capture this list by giving
whos
an output variable:

>> varlist = whos

varlist =

5x1 struct array with fields:

name

size

bytes

class

The average size of the variables is

>> mean([varlist.bytes])

ans =

140

A cell array of variable names can be generated by:

>> names = {varlist.name}

names =

'a'

'acell'

'meteo'

'name'

'vect'

Similar structures are generated by giving output arguments to
what

and
dir
.

29 Multidimensional Arrays

Multidimensional matrices are natural extensions of the normal two-

dimensional matrices for cases where the data represent more than two

dimensions. Examples are

•

Medical tomography, where three-dimensional volumetric data are

built up from a series of two-dimensional images;

•

Temperature measurements taken at a three-dimensional grid in a

room;

•

Temperature measurements taken at a three-dimensional grid in

a room and at a sequence of times, leading to a four-dimensional

data set;

•

Red, green and blue components of a two-dimensional image, an

M

×

N

×

3 matrix; and

•

Acoustic measurements of sound spectra as a function of frequency,

direction of arrival, and time (sonar).

Let us get the hang of things by generating a 3

×

3

×

3 matrix: