Getting Started with MATLAB
Welcome to this MATLAB Video tutorial. If you have never used MATLAB before, this demonstration will get you started and show you where to go to next to learn more.
Contents
Creating Variables
The MATLAB language lets you construct commands to create and process variables. You can create variables by entering them in the command window here. For example,
a = 1
a =
1
b = 2
b =
2
c = a+b
c =
3
or...
d = cos(a)
d =
0.5403
Creating Vectors
MATLAB is an array based language where variables can be vectors, matrices or N dimensional arrays. You use square brackets to construct arrays. To create a row vector you can type,
t=[1 2 3 4 5]
t =
1 2 3 4 5
You can use the colon operator to simplify the creation of equally spaced arrays.
t = 1:5 % t equals 1 to 5
t =
1 2 3 4 5
You can recall previously entered commands by dragging them from the command history here or by pressing the up-arrow key. You can then edit it...
t=0:.01:1 % t goes from 0 in steps of .01 to 1
t =
Columns 1 through 6
0 0.0100 0.0200 0.0300 0.0400 0.0500
Columns 7 through 12
0.0600 0.0700 0.0800 0.0900 0.1000 0.1100
Columns 13 through 18
0.1200 0.1300 0.1400 0.1500 0.1600 0.1700
Columns 19 through 24
0.1800 0.1900 0.2000 0.2100 0.2200 0.2300
Columns 25 through 30
0.2400 0.2500 0.2600 0.2700 0.2800 0.2900
Columns 31 through 36
0.3000 0.3100 0.3200 0.3300 0.3400 0.3500
Columns 37 through 42
0.3600 0.3700 0.3800 0.3900 0.4000 0.4100
Columns 43 through 48
0.4200 0.4300 0.4400 0.4500 0.4600 0.4700
Columns 49 through 54
0.4800 0.4900 0.5000 0.5100 0.5200 0.5300
Columns 55 through 60
0.5400 0.5500 0.5600 0.5700 0.5800 0.5900
Columns 61 through 66
0.6000 0.6100 0.6200 0.6300 0.6400 0.6500
Columns 67 through 72
0.6600 0.6700 0.6800 0.6900 0.7000 0.7100
Columns 73 through 78
0.7200 0.7300 0.7400 0.7500 0.7600 0.7700
Columns 79 through 84
0.7800 0.7900 0.8000 0.8100 0.8200 0.8300
Columns 85 through 90
0.8400 0.8500 0.8600 0.8700 0.8800 0.8900
Columns 91 through 96
0.9000 0.9100 0.9200 0.9300 0.9400 0.9500
Columns 97 through 101
0.9600 0.9700 0.9800 0.9900 1.0000
Adding a semicolon avoids command output being echoed to the command window.
t=0:.01:1;
The whos Command and WSB
To see what variables you have created so far type,
whos
Name Size Bytes Class Attributes a 1x1 8 double b 1x1 8 double c 1x1 8 double d 1x1 8 double t 1x101 808 double
...or view a list in the workspace browser here
To see the value of a variable just type its name such as,
b
b =
2
Vector Operations
You carry-out operations on vectors just like simple scalars. For example,
y = sin(2*pi*t)
y =
Columns 1 through 6
0 0.0628 0.1253 0.1874 0.2487 0.3090
Columns 7 through 12
0.3681 0.4258 0.4818 0.5358 0.5878 0.6374
Columns 13 through 18
0.6845 0.7290 0.7705 0.8090 0.8443 0.8763
Columns 19 through 24
0.9048 0.9298 0.9511 0.9686 0.9823 0.9921
Columns 25 through 30
0.9980 1.0000 0.9980 0.9921 0.9823 0.9686
Columns 31 through 36
0.9511 0.9298 0.9048 0.8763 0.8443 0.8090
Columns 37 through 42
0.7705 0.7290 0.6845 0.6374 0.5878 0.5358
Columns 43 through 48
0.4818 0.4258 0.3681 0.3090 0.2487 0.1874
Columns 49 through 54
0.1253 0.0628 0.0000 -0.0628 -0.1253 -0.1874
Columns 55 through 60
-0.2487 -0.3090 -0.3681 -0.4258 -0.4818 -0.5358
Columns 61 through 66
-0.5878 -0.6374 -0.6845 -0.7290 -0.7705 -0.8090
Columns 67 through 72
-0.8443 -0.8763 -0.9048 -0.9298 -0.9511 -0.9686
Columns 73 through 78
-0.9823 -0.9921 -0.9980 -1.0000 -0.9980 -0.9921
Columns 79 through 84
-0.9823 -0.9686 -0.9511 -0.9298 -0.9048 -0.8763
Columns 85 through 90
-0.8443 -0.8090 -0.7705 -0.7290 -0.6845 -0.6374
Columns 91 through 96
-0.5878 -0.5358 -0.4818 -0.4258 -0.3681 -0.3090
Columns 97 through 101
-0.2487 -0.1874 -0.1253 -0.0628 -0.0000
This makes use of the constant pi, pre-defined in MATLAB.
Basic Plotting
You can plot y against t with...
plot(t,y) % the plot command.
Complex Numbers
In MATLAB, variables can be complex; with i used to denote the imaginary part such as...
x= 3 + 4i
x = 3.0000 + 4.0000i
Creating Matrices
You enter matrices using the semicolon in the following way,
a = [1 2 3; 4 5 6; 7 8 10]
a =
1 2 3
4 5 6
7 8 10
...or you can use functions.
Function Browser and Hints
You can browse a list of available functions in MATLAB by clicking this icon, and browsing functions by category or by searching using keywords here. Here we will generate a matrix of random numbers. Double clicking enters the function name.
Pausing after typing a parentheses shows a list of possible arguments
data=rand(5,5)
data =
0.7577 0.7060 0.8235 0.4387 0.4898
0.7431 0.0318 0.6948 0.3816 0.4456
0.3922 0.2769 0.3171 0.7655 0.6463
0.6555 0.0462 0.9502 0.7952 0.7094
0.1712 0.0971 0.0344 0.1869 0.7547
Help
You can access help on all of MATLAB by clicking on the question mark here, then browse or search for information.
Accessing Demonstrations
You can access demonstrations and getting started documentation from this message bar.
You can find the dimensions of an array with the size function.
size(data)
ans =
5 5
...which is also shown in the workspace browser.
Matrix Operations
You can perform matrix operations such as...
b = a' % b = the transpose of a.
b =
1 4 7
2 5 8
3 6 10
c = a*b % c = a times b, which performs matrix multiplication,...
c =
14 32 53
32 77 128
53 128 213
...or
c = a.*b % c = a dot times b
c =
1 8 21
8 25 48
21 48 100
...which performs element-wise multiplication, where the corresponding elements of each matrix are multiplied.
You could calculate the inverse of matrix a...
inv(a)
ans =
-0.6667 -1.3333 1.0000
-0.6667 3.6667 -2.0000
1.0000 -2.0000 1.0000
inv(a)*a % and multiply this by a...
ans =
1.0000 0 0.0000
0 1.0000 0
-0.0000 -0.0000 1.0000
...to confirm you get the identity matrix.
Indexing
You can select elements or sections of an array by indexing. For the variable a,
a
a =
1 2 3
4 5 6
7 8 10
Here is the value at...
a(2,3) % ...the second row and third column
ans =
6
Or for the variable data,
data
data =
0.7577 0.7060 0.8235 0.4387 0.4898
0.7431 0.0318 0.6948 0.3816 0.4456
0.3922 0.2769 0.3171 0.7655 0.6463
0.6555 0.0462 0.9502 0.7952 0.7094
0.1712 0.0971 0.0344 0.1869 0.7547
...here is the section from,
data(1:3,2:end) % rows 1 to 3 and columns 2 to the end.
ans =
0.7060 0.8235 0.4387 0.4898
0.0318 0.6948 0.3816 0.4456
0.2769 0.3171 0.7655 0.6463
You can set values in this way too. For example, with data, you could
data(1:2, :) = 0 % set rows 1:2 and all the columns to zero.
data =
0 0 0 0 0
0 0 0 0 0
0.3922 0.2769 0.3171 0.7655 0.6463
0.6555 0.0462 0.9502 0.7952 0.7094
0.1712 0.0971 0.0344 0.1869 0.7547
The colon operator used on its own in indexing, specifies "all elements", in this case, all columns.
Note that array indices in MATLAB start at 1.
Plotting Matrices
And you can plot matrices as well. If you wanted to display the matrix w...
w=y'*y; % ...generated by multiplying the transpose of the sine wave vector y, with itself...
...you could enter...
surf(w);
...which creates a surface plot.
Conclusion
That concludes the demonstration. You can try some of these examples in MATLAB now or watch one of the other videos.