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:
