# Difference between revisions of "MatlabIntro"

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** 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: | ** 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: | ||

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## Revision as of 11:29, 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