[index]
Index function.
Syntax
expr [index_1] [index_2]
Operands
- expr
- A valid vector, matrix, string, or string array expression.
- index_1
- Either a scalar expression that describes the position of an element in a vector or vector expression that describes the position of a row of elements in a matrix.
- index_2
- An optional scalar or vector expression that describes the position of an element of a matrix.
Example
| Expression | Result |
|---|---|
a = {4, 2, 6,
8}
|
6 |
{1, 2, 3, 4} [0] |
1 |
{2, 4, 6, 8} [{1, 2}] |
{4,6} |
{ {1, 2, 3,}, {4, 5, 6} } [1] |
{4, 5, 6} |
{ {1, 2, 3,}, {4, 5, 6} } [1] [0] |
4 |
{"The ", "quick ", "brown ", "fox"}
[2] |
"brown" |
| Expression | Result |
|---|---|
x = c1.x[0:100:1]
|
A curve is created which is the first 101 points of
c1. |
Comments
[index] is the only mathematical function where brackets, [ ], do not indicate optional items. The brackets are part of this function's syntax.
The index function accesses specific elements of a vector or matrix expression.
The first element of a vector is at index zero. index_1 and index_2 must be non-negative and less than the total number of elements in the vector expression.
If expr is a vector, the result is the scalar located at the index_1 position.
If expr is a matrix, the result is the row vector located at the index_1 position. A second index can be used to identify the scalar at the index_2 position of the index_1 vector.
If expr is a string array, the result is the string located at the index_1 position. A second index cannot be used to identify characters within the string array.