Yet you would be surprised how many beginners, preferring to rush
straight to the computer, start with step 2 instead of step 1

It is well worth developing the mental discipline of structure-
planning your program first. You could even use cut and paste to
plan as follows:
1.
Type the structure plan into the Editor (each line preceded by %
as shown above).
2.
Paste a second copy of the plan directly below the first.
3.
Translate each line in the second copy into a MATLAB statement,
or statements (add % comments as in the example below).
4.
Finally,
paste
all the translated
MATLAB
statements
into the
Command Window, and run them.
5.
If necessary,
go back to the Editor to make corrections,
and
repaste the corrected statements to the Command Window (or save
the program in the Editor as an M-file and execute it).

You might like to try this as an exercise,
before looking at the final
program, which is as follows:
% Vertical motion under gravity
g = 9.8;
% acceleration due to gravity
u = 60;
% initial velocity (meters/sec)
t = 0 : 0.1 : 12.3; % time in seconds
s = u * t -
g / 2 * t .ˆ 2;
% vertical
displacement in meters
plot(t, s), title( ’Vertical motion under
gravity’ ), ...
xlabel
( ’time’ ),
ylabel(
’vertical displacement’ ), grid
disp
( [t’ s’] )
% display a table

Note the following points:
Anything in a line following the percentage symbol
%
is ignored by
MATLAB and may be used as a comment (description).
The statement
t = 0 : 0.1 : 12.3
sets up a vector.
The formula for
s
is evaluated
for every element
of the vector
t
,
making another vector.
The expression
t.ˆ2 squares
each element
in t. This is called an
array operation
, and is different to squaring the vector itself,
which
is a
matrix
operation, as we shall see later.
More than one statement can be entered on the same line if the
statements are separated by commas.
A statement or group of statements can be continued to the next
line with an
ellipsis
of three or more dots ...
The statement disp
(*t’ s’+) first transposes the row vectors t and s
into columns, and constructs
a matrix from these two columns,
which is then displayed.

You might want to save the program under a helpful name, like
throw.m
if you think you might come back to it. In that case,
it
would be worth keeping the structure plan as part of the file; just
insert
%
symbols in front of each line of the structure plan. This
way, the structure plan reminds you what the program does when
you look at it again after some months. Note that you can use the
context menu in the Editor to Comment/Uncomment a block of
selected text.

Operators, expressions and statements
Any program worth its salt actually does something.
What it basically
does is to evaluate
expressions
, such as
u*t - g/2*t.
ˆ
2
and to execute (carry out) statements,
such as
balance = balance + interest
MATLAB has been described as
“
an
expression
based language
. It
interprets and evaluates typed expressions.
”
Expressions
are
constructed from a variety of things, such as
numbers, variables, and
operators.