More
MATLAB Commands...
On this page we present the
use of some very basic MATLAB commands and functions. With
Matlab, you can perform
simple operations, as if you were working with a calculator.
Operation |
Symbol |
Example |
Addition,
a+b |
+ |
5
+ 3 |
Subtraction,
a-b |
- |
20 - 9 |
Multiplication,
ab |
* |
8.7
* 9.2 |
Division,
a/b |
/ |
40
/ 8 |
Power,
ab |
^ |
5^3
|
Common
Functions
abs(x) |
absolute value |
acos(x) |
inverse
cosine, result in radians |
angle(x) |
angle of
complex number |
asin(x) |
inverse sine,
result in radians |
atan(x) |
inverse tangent |
ceil(x) |
round towards
plus infinity |
conj(x) |
complex
conjugate |
cos(x) |
cosine |
exp(x) |
exponential |
fix(x) |
round towards
zero |
floor(x) |
round towards
minus infinity |
imag(x) |
complex
imaginary part |
log(x) |
natural
logarithm |
log10(x) |
common (base
10) logarithm |
real(x) |
complex real
part |
round(x) |
round towards
nearest integer |
sign(x) |
signum function |
sin(x) |
sine |
sqrt(x) |
square root |
tan(x) |
tangent |
Matlab
doesn't care about spaces between operands, and multiplications are
performed before additions. Type these operations on the command window
(only the
part just after '>>', and Matlab will give the answers):
>> 2 + 1 + 3
ans =
6
>> 8*9 - 6*5 + 3*4
ans =
54
>> x=2
x =
2
>> y=3
y =
3
>> cos(x)+sqrt(y)+tan(x+y)
ans =
-2.0646
>>
You can keep values in variables:
>> apples=2
apples =
2
>> bananas=5
bananas =
5
>> peaches=4
peaches =
4
>> fruit=apples+bananas+peaches
fruit =
11
Ending the instruction with a ';' sign tells Matlab to make the
operation but not to display the answer.
To see a list of your variables in memory you can use the commands
'who' or 'whos'.
>> whos
Name |
Size |
Bytes |
Class |
|
|
|
|
|
|
ans |
1x1 |
8 |
double |
array |
apples |
1x1 |
8 |
double |
array |
bananas |
1x1 |
8 |
double |
array |
fruit |
1x1 |
8 |
double |
array |
peaches |
1x1 |
8 |
double |
array |
Grand total is 5 elements using 40 bytes
Variables are sensitive to lower/upper case. They have to start with a
letter and can contain also numbers and underscores.
Special
Names |
Value |
ans |
Default
for results |
pi |
3.141592... |
eps |
Smallest
possible number in Matlab |
inf |
Infinite |
NaN |
Not
a number |
i |
square
root of -1 |
j |
square
root of -1 |
To delete variables you can use the 'clear' command.
Operations with Complex
Numbers
>> c1 = 1 - 2i
c1 =
1.0000 - 2.0000i
>> c2 = 6 - 9j
c2 =
6.0000 - 9.0000i
>> c3 = sqrt(-2)
c3 =
0 + 1.4142i
>> c4 = c1 + c2 - c3
c4 =
7.0000 -12.4142i
>>
M-files
Matlab
allows you to place your commands on a simple text file. You should
name this file with the '.m' extension. Giving Matlab the name of this
file while in the command window, makes Matlab to execute the script.
For example, name
a text file 'primer.m'.
Make it contain the following text:
a = 3; b = -4; c = 8;
d = a*b-c
When you execute this from the command window
>> primer
you obtain this information from MATLAB:
d =
-20
M-File
functions
disp(ans) |
show results
without showing the variable name |
input |
prompt for
user input |
keyboard |
stops
execution of the m-file and gives control to the
user's keyboard ('return' to quit) |
pause |
causes a
procedure to stop and wait for the user to
strike any key before continuing |
pause(n) |
pauses for n
seconds |
waitforbuttonpress |
wait for
key/buttonpress over figure |
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