Graphics Programs Reference
In-Depth Information
If you have not previously defined
u
, then typing
scriptex2
will produce an
error message. However, if you type
scriptex2
after running
scriptex1
,
then the definition of
u
from the first script will be used in the second script
and the output
n=4
will be displayed.
Ifyoudon'twanttheoutputofascriptM-filetodependonanyearliercompu-
tations in your MATLAB session, put the line
clear all
near the beginning
of the M-file, as we suggested in
Structuring Script M-files
in Chapter 3.
Variables in Function M-Files
The variables used in a function M-file are
local
, meaning that they are un-
affected by, and have no effect on, the variables in your Workspace. Consider
the following function M-file, called
sq.m:
function z = sq(x)
% sq(x) returns the square of x.
z = x.ˆ2;
Typing
sq(3)
produces the answer
9
, whether or not
x
or
z
is already defined
in your Workspace, and neither defines them, nor changes their definitions, if
they have been previously defined.
Structure of Function M-Files
The first line in a function M-file is called the
functiondefinitionline
; it defines
the function name, as well as the number and order of input and output argu-
ments. Following the function definition line, there can be several comment
lines that begin with a percent sign (
%
). These lines are called
help text
and
are displayed in response to the command
help
. In the M-file
sq.m
above,
there is only one line of help text; it is displayed when you type
help sq
.
The remaining lines constitute the
function body
; they contain the MATLAB
statements that calculate the function values. In addition, there can be com-
ment lines (lines beginning with
%
) anywhere in an M-file. All statements in
a function M-file that normally produce output should end with a semicolon
to suppress the output.
Function M-files can have multiple input and output arguments. Here is
an example, called
polarcoordinates.m
, withtwo input and two output
arguments:
function [r, theta] = polarcoordinates(x, y)
% polarcoordinates(x, y) returns the polar coordinates
% of the point with rectangular coordinates (x, y).
Search WWH ::
Custom Search