# Special Characters [ ] ( ) = ' . , `; % !`

## Purpose

Special characters.

## Synopsis

    [ ] ( ) = ' . , ; % !

## Description

`[ ]`
  Brackets are used to form vectors and matrices. `[6.9 9.64 sqrt(-1)]` is a vector with three elements separated by blanks. `[6.9, 9.64, i]` is the same thing. [`1+j 2-j 3]` and `[1 +j 2` -`j 3]` are not the same. The first has three elements, the second has five.

  `[11 12 13; 21 22 23]` is a 2-by-3 matrix. The semicolon ends the first row.
  Vectors and matrices can be used inside `[ ]` brackets. `[A B;C]` is allowed if the number of rows of `A` equals the number of rows of `B` and the number of columns of `A` plus the number of columns of `B` equals the number of columns of `C`. This rule generalizes in a hopefully obvious way to allow fairly complicated constructions.
  `A = [ ]` stores an empty matrix in `A`.
  For the use of `[` and `]` on the left of an "`=`" in multiple assignment statements, see `lu`, `eig`, `svd`, and so on.

`( )`
  Parentheses are used to indicate precedence in arithmetic expressions in the usual way. They are used to enclose arguments of functions in the usual way. They are also used to enclose subscripts of vectors and matrices in a manner somewhat more general than usual. If `X` and `V` are vectors, then `X(V)` is `[X(V(1)), X(V(2)), ..., X(V(n))]`. The components of `V` are rounded to nearest integers and used as subscripts. An error occurs if any such subscript is less than `1` or greater than the dimension of `X`. Some examples are

  `X(3)` is the third element of `X`.
  `X([1 2 3])` is the first three elements of `X`.
  `X([sqrt(2) sqrt(3) 4*atan(1)])` is also the first three elements of `X`.
  If `X` has `n` components, `X(n:`-`1:1)` reverses them. The same indirect subscripting works in matrices. If `V` has `m` components and `W` has `n` components, then `A(V,W)` is the m-by-`n` matrix formed from the elements of `A` whose subscripts are the elements of `V` and `W`. For example, `A([1,5],:) = A([5,1],:)` interchanges rows `1` and `5` of `A`.

`=`
  Used in assignment statements. `==` is the relational EQUALS operator. See the Relational Operators page.
`'`
  Matrix transpose. `X'` is the complex conjugate transpose of `X`. `X.'` is the nonconjugate transpose.

  Quote. `'any text'` is a vector whose components are the ASCII codes for the characters. A quote within the text is indicated by two quotes.

`.`
  Decimal point. `314/100`, `3.14` and `.314e1` are all the same.

  Element-by-element operations are obtained using `.*` `,` .^ , `./` , or `.\`. See the Arithmetic Operators page.
  Three or more points at the end of a line indicate continuation.

`,`
  Comma. Used to separate matrix subscripts and function arguments. Used to separate statements in multistatement lines. For multi-statement lines, the comma can be replaced by a semicolon to suppress printing.
`;`
  Semicolon. Used inside brackets to end rows. Used after an expression or statement to suppress printing or separate statements.
`%`
  Percent. The percent symbol denotes a comment; it indicates a logical end of line. Any following text is ignored.
`!`
  Exclamation point. Indicates that the rest of the input line is issued as a command to the operating system.

## See Also

Arithmetic, relational, and logical operators.

(c) Copyright 1994 by The MathWorks, Inc.