Difference between revisions of "MatlabIntro"
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| − | === Vector and Matrices | + | * 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> | ||
| + | >> % This is a comment | ||
| + | >> x = 0; % this is another comment | ||
| + | </pre> | ||
| + | |||
| + | |||
| + | * Functions may return more than one value, and they can be of any type. For example: | ||
| + | |||
| + | <pre> | ||
| + | [r,c] = size([ones(2)]) | ||
| + | |||
| + | r = | ||
| + | |||
| + | 2 | ||
| + | |||
| + | |||
| + | c = | ||
| + | |||
| + | 2 | ||
| + | </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> | ||
| Line 42: | Line 66: | ||
</pre> | </pre> | ||
| − | and they both generate a row vector. Semi-colons, instead, separate elements column-wise: | + | and they both generate a row vector. Semi-colons, instead, separate elements column-wise. For example, the following line will create a column vector: |
<pre> | <pre> | ||
>> x = [1;2;3;4;5] | >> x = [1;2;3;4;5] | ||
| + | </pre> | ||
| + | |||
| + | |||
| + | * You can combine both to create a bigger matrix: | ||
| + | |||
| + | <pre> | ||
| + | >> x = [1 2 3 4;2 3 4 5;3 4 5 6] | ||
| + | |||
| + | x = | ||
| + | |||
| + | 1 2 3 4 | ||
| + | 2 3 4 5 | ||
| + | 3 4 5 6 | ||
| + | |||
| + | </pre> | ||
| + | |||
| + | * Some useful vector/matrix operators are: | ||
| + | |||
| + | In the following code snippets I'll assume that x was defined as: | ||
| + | <pre> | ||
| + | >> x = [1 2;3 4] | ||
| + | |||
| + | 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> | </pre> | ||
Revision as of 11:07, 21 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
>> x = 1
x =
1
vs.
>> x = 1; >>
- 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
- Functions may return more than one value, and they can be of any type. For example:
[r,c] = size([ones(2)])
r =
2
c =
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, separate elements column-wise. For example, the following line will create a column vector:
>> x = [1;2;3;4;5]
- You can combine both to create a bigger matrix:
>> x = [1 2 3 4;2 3 4 5;3 4 5 6]
x =
1 2 3 4
2 3 4 5
3 4 5 6
- Some useful vector/matrix operators are:
In the following code snippets I'll assume that x was defined as:
>> x = [1 2;3 4]
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
General tips
- Try to vectorize every operation if you can
