Graphics Programs Reference
In-Depth Information
function y = absval(x)
y=x;
ify<0
y = -y;
end
The
elseif
statement is useful if there are more than two alternatives
and they can be distinguished by a sequence of true/false tests. It is essen-
tially equivalent to an
else
statement followed immediately by a nested
if
statement.Intheexamplebelow,weuse
elseif
inanM-file
signum.m
,which
evaluates the mathematical function
1
x
>
0
,
0
x
=
0
,
−
1
x
<
0
.
sgn(
x
)
=
(Again, MATLAB has a built-in function
sign
that performs this function for
more general inputs than we consider here.)
function y = signum(x)
ifx>0
y=1;
elseif x == 0
y=0;
else
y = -1;
end
Here if the input
x
is positive, then the output
y
is set to
1
and all commands
from the
elseif
statement to the
end
statement are skipped. (In particular,
the test in the
elseif
statement is not performed.) If
x
is not positive, then
MATLABskipstothe
elseif
statementandteststoseeif
x
equals
0
.Ifso,
y
is
set to
0
; otherwise
y
is set to
-1
. Notice that MATLAB requires a double equal
sign
==
to test for equality; a single equal sign is reserved for the assignment
of values to variables.
Like
for
and the other programming commands you will encounter,
if
and
its associated commands can be used in the Command Window. Doing so can
be useful for practice with these commands, but they are intended mainly for
use in M-files. In our discussion of branching, we consider primarily the case
of function M-files; branching is less often used in script M-files.
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