Difference between revisions of "MatlabIntro"
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* Use semi-colon at the end of the line to prevent the output of the operation to be printed to the screen | * Use semi-colon at the end of the line to prevent the output of the operation to be printed to the screen | ||
| + | |||
| + | * Comments are specified using % at the beginning of the comment. Only line comments are allowed (sorry, but no block-comments, although there's a shortcut in the editor to comment out all the selected lines) | ||
<pre> | <pre> | ||
| − | + | % This is a comment | |
| + | x = 0; % this is another comment | ||
| + | </pre> | ||
| − | + | * MATLAB is not strongly typed. The following sequence of commands is valid: | |
| − | + | <pre> | |
| + | x = 1; | ||
| + | x = "this is a string" | ||
</pre> | </pre> | ||
| − | + | * Functions may return more than one value, and they can be of any type. For example: | |
<pre> | <pre> | ||
| − | + | [r,c] = size([ones(2)]) | |
| − | + | ||
</pre> | </pre> | ||
| − | + | == Vector and Matrices == | |
* Use square brackets to define a vector/matrix | * Use square brackets to define a vector/matrix | ||
| − | < | + | <pre> |
x = [1 2 3 4 5] | x = [1 2 3 4 5] | ||
| − | </ | + | </pre> |
| − | * Inside a vector/matrix definition, commas or spaces separate elements row-wise | + | * Inside a vector/matrix definition, commas or spaces separate elements row-wise. For example: |
<pre> | <pre> | ||
| − | + | x = [1 2 3 4 5] | |
</pre> | </pre> | ||
| Line 39: | Line 44: | ||
<pre> | <pre> | ||
| − | + | x = [1,2,3,4,5] | |
</pre> | </pre> | ||
| − | and they both generate a row vector. Semi-colons, instead, | + | and they both generate a row vector. Semi-colons, instead, indicate the end of a row. For example, the following line will create a column vector: |
<pre> | <pre> | ||
| − | + | x = [1;2;3;4;5] | |
</pre> | </pre> | ||
| + | |||
| + | |||
| + | * You can combine both to create a matrix: | ||
| + | |||
| + | <pre> | ||
| + | x = [1 2 3 4;2 3 4 5;3 4 5 6] | ||
| + | </pre> | ||
| + | |||
| + | * Some useful vector/matrix operators are: | ||
| + | |||
| + | The following code snippets assume that x was defined as: | ||
| + | <pre> | ||
| + | x = [1 2;3 4] | ||
| + | </pre> | ||
| + | |||
| + | ** Use ' as a suffix to transpose the vector/matrix: | ||
| + | <pre> | ||
| + | >> x' | ||
| + | |||
| + | ans = | ||
| + | |||
| + | 1 3 | ||
| + | 2 4 | ||
| + | >> | ||
| + | </pre> | ||
| + | ** The function size(x) will return the size of x: first number is the number of row and the second is the number of columns: | ||
| + | <pre> | ||
| + | >> size(x) | ||
| + | |||
| + | ans = | ||
| + | |||
| + | 2 2 | ||
| + | </pre> | ||
| + | |||
| + | ** You can access individual elements of a matrix using parenthesis (first argument specifies the row and the second specifies the column): | ||
| + | <pre> | ||
| + | >> x(2,1) | ||
| + | |||
| + | ans = | ||
| + | |||
| + | 3 | ||
| + | </pre> | ||
| + | |||
| + | == Plotting == | ||
| + | |||
| + | The basic command is plot(x), to plot the contents of x (if x is a matrix, then each column is plotted as a different line): | ||
| + | |||
| + | <pre> | ||
| + | fs = 441000; | ||
| + | t = 0:1/fs:0.01; | ||
| + | plot(sin(2*pi*220*t)); | ||
| + | </pre> | ||
| + | |||
| + | You can also use plot(x,y): | ||
| + | |||
| + | <pre> | ||
| + | plot(t, sin(2*pi*220*t)); | ||
| + | </pre> | ||
| + | |||
| + | By default plot will erase the previous plot before drawing the new one. Use hold to prevent this from happening. Also, you can use a third argument to specify the line color (and other plotting options): | ||
| + | |||
| + | <pre> | ||
| + | hold on; | ||
| + | plot(t, sin(2*pi*110*t), 'r'); | ||
| + | plot(t, sin(2*pi*330*t), 'g'); | ||
| + | plot(t, sin(2*pi*440*t), 'k'); | ||
| + | hold off | ||
| + | </pre> | ||
| + | |||
| + | == Sound == | ||
| + | |||
| + | |||
== General tips == | == General tips == | ||
Latest revision as of 15:09, 22 September 2010
Basics
- Use semi-colon at the end of the line to prevent the output of the operation to be printed to the screen
- Comments are specified using % at the beginning of the comment. Only line comments are allowed (sorry, but no block-comments, although there's a shortcut in the editor to comment out all the selected lines)
% This is a comment x = 0; % this is another comment
- MATLAB is not strongly typed. The following sequence of commands is valid:
x = 1; x = "this is a string"
- Functions may return more than one value, and they can be of any type. For example:
[r,c] = size([ones(2)])
Vector and Matrices
- Use square brackets to define a vector/matrix
x = [1 2 3 4 5]
- Inside a vector/matrix definition, commas or spaces separate elements row-wise. For example:
x = [1 2 3 4 5]
is the same as:
x = [1,2,3,4,5]
and they both generate a row vector. Semi-colons, instead, indicate the end of a row. For example, the following line will create a column vector:
x = [1;2;3;4;5]
- You can combine both to create a matrix:
x = [1 2 3 4;2 3 4 5;3 4 5 6]
- Some useful vector/matrix operators are:
The following code snippets assume that x was defined as:
x = [1 2;3 4]
- Use ' as a suffix to transpose the vector/matrix:
>> x'
ans =
1 3
2 4
>>
- The function size(x) will return the size of x: first number is the number of row and the second is the number of columns:
>> size(x)
ans =
2 2
- You can access individual elements of a matrix using parenthesis (first argument specifies the row and the second specifies the column):
>> x(2,1)
ans =
3
Plotting
The basic command is plot(x), to plot the contents of x (if x is a matrix, then each column is plotted as a different line):
fs = 441000; t = 0:1/fs:0.01; plot(sin(2*pi*220*t));
You can also use plot(x,y):
plot(t, sin(2*pi*220*t));
By default plot will erase the previous plot before drawing the new one. Use hold to prevent this from happening. Also, you can use a third argument to specify the line color (and other plotting options):
hold on; plot(t, sin(2*pi*110*t), 'r'); plot(t, sin(2*pi*330*t), 'g'); plot(t, sin(2*pi*440*t), 'k'); hold off
Sound
General tips
- Try to vectorize every operation if you can
