Graphics Programs Reference
In-Depth Information
1.5 The Colon Operator
To generate a vector of equally-spaced elements matlab provides the
colon operator. Try the following commands:
1:5
0:2:10
0:.1:2*pi
The syntax
x
:
y
means roughly “generate the ordered set of numbers
from
x
to
y
with increment 1 between them.” The syntax
x
:
d
:
y
means
roughly “generate the ordered set of numbers from
x
to
y
with increment
d
between them.”
1.6 Linspace
To generate a vector of evenly spaced points between two end points,
you can use the function
linspace(
start
,
stop
,
npoints
)
:
>> x = linspace(0,1,10)
x=
Columns 1 through 7
0 0.1111 0.2222 0.3333 0.4444 0.5556 0.6667
Columns 8 through 10
0.7778 0.8889 1.0000
generates 10 evenly spaced points from 0 to 1. Typing
linspace(
start
,
stop
)
will generate a vector of 100 points.
1.7 Plotting Vectors
Whereas other computer languages, such as Fortran, work on numbers
one at a time, an advantage of matlab is that it handles the matrix as
a single unit. Let us consider an example that shows why this is useful.
Imagine you want to plot the function
y
= sin
x
for
x
between 0 and 2
π
.
A Fortran code to do this might look like this:
DIMENSION X(100),Y(100)
PI = 4*ATAN(1)
DO 100 I = 1,100
X(I) = 2*PI*I/100
Y(I) = SIN(X(I))
100 CONTINUE
PLOT(X,Y)
Here we assume that we have access to a Fortran plotting package
in which
PLOT(X,Y)
makes sense. In matlab we can get our plot by
typing:
