  # 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  