Using Simulink

Look-Up Table (2-D)

Perform piecewise linear mapping of two inputs.

Library

Functions & Tables

Description

The Look-Up Table (2-D) block maps the block inputs to an output using linear interpolation of a table of values defined by the block's parameters.

You define the possible output values as the Table parameter. You define the values that correspond to its rows and columns with the Row and Column parameters. The block generates an output value by comparing the block inputs with the Row and the Column parameters. The first input identifies a row, and the second input identifies a column, as shown by this figure.

The block generates output based on the input values:

• If the inputs match row and column parameter values, the output is the table value at the intersection of the row and column.
• If the inputs do not match row and column parameter values, the block generates output by linearly interpolating between the appropriate table values. If either or both block inputs are less than the first or greater than the last row or column parameter values, the block extrapolates from the first two or last two points.

If either the Row or Column parameter has a repeating value, the block chooses a value using the technique described for the Look-Up Table block.

The Look-Up Table block allows you to map a single input value into a vector of output values (see Look-Up Table).

Example

In this example, the block parameters are defined as:

Row:      [1 2]
Column:   [3 4]
Table:    [10 20; 30 40]

The first figure shows the block outputting a value at the intersection of block inputs that match row and column values. The first input is 1 and the second input is 4. These values select the table value at the intersection of the first row (row parameter value 1) and second column (column parameter value 4).

In the second figure, the first input is 1.7 and the second is 3.4. These values cause the block to interpolate between row and column values, as shown in the table at the left. The value at the intersection (28) is the output value.

Data Type Support

A Look-Up Table (2-D) block accepts and outputs signals of type double.

Parameters and Dialog Box

Row

The row values for the table, entered as a vector. The vector values must increase monotonically.

Column

The column values for the table, entered as a vector. The vector values must increase monotonically.

Table

The table of output values. The matrix size must match the dimensions defined by the Row and Column parameters.

Characteristics

Direct Feedthrough	Yes
Sample Time	Inherited from driving blocks
Scalar Expansion	Of one input if the other is a vector
Dimensionalized	Yes
Zero Crossing	No

Look-Up Table

Look-Up Table (n-D)