Graphics Programs Reference

In-Depth Information

>> v6

v6 =

1

2

3

4

5

6

The
feval
Function

The
feval
command is like
eval
, except that it is used for evaluating

named functions. An example would be:

str = 'sin';

t = linspace(0,2*pi);

q = feval(str,t);

plt(t,q)

If
str
is a string containing the name of a function, then
y=

feval(str,x)
evaluates that function for the input argument
x
.

Another example defines data for plotting by looping over the trigono-

metric functions
sin
,
cos
, and
tan
contained within a single matrix of

characters (the command
zeroaxes
is part of the companion software

to this topic):

str = ['sin';'cos';'tan'];

for i = 1:3

q(i,:) = feval(str(i,:),t);

end

clf

plt(t,q)

axis([0 2*pi -6 6])

zeroaxes

Inline Objects

Inline objects allow you to store a function as a string and use it much

as you would write it symbolically. This, for example, is how to define

the parabola
f
(
x
)=(
x
+ 1)(
x

−

1):

>> f = inline('(x + 1).*(x - 1)')

f=

Inline function:

f(x) = (x + 1).*(x - 1)

We can now evaluate
f
(3) by typing:

>> f(3)

ans =

8