Graphics Programs Reference
In-Depth Information
>> s = 100*spiral(3)
s=
700 800 900
600 100 200
500 400 300
>> ind = find(s>400)
ind =
1
2
3
4
7
>> s(ind)
ans =
700
600
500
800
900
>> s(s>400)
ans =
700
600
500
800
900
After introducing graphics of functions of two variables in the next sec-
tion, we will see how the
find
command can be used to do the three-
dimensional equivalent of the plot shown on page 23, where the domain
of a curve satisfying a logical test was extracted.
7 Graphics of Functions of Two Variables
7.1 Basic Plots
A matlab surface is defined by the
z
coordinates associated with a set
of (
x, y
) coordinates. For example, suppose we have the set of (
x, y
)
coordinates:
1
,
12
,
13
,
14
,
1
1
,
22
,
23
,
24
,
2
1
,
32
,
33
,
34
,
3
1
,
42
,
43
,
44
,
4
(
x, y
)=
.
The points can be plotted as (
x, y
) pairs:
