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# Adaptive Lookup Table (2D Stair-Fit)

## Description

The Adaptive Lookup Table (2D Stair-Fit) block creates a two-dimensional adaptive lookup table by dynamically updating the underlying lookup table. The block uses the outputs, y, of your system to do the adaptations.

Each indexing parameter u may take a value within a set of adapting data points, which are called breakpoints. Two breakpoints in each dimension define a cell. The set of all breakpoints in one of the dimensions defines a grid. In the two-dimensional case, each cell has four breakpoints and is a flat surface.

You can use the Adaptive Lookup Table (2D Stair-Fit) block to model time-varying systems with two inputs.

Doubles only

## Dialog Box

First input (row) breakpoint set

The vector of values containing possible block input values for the first input variable. The first input vector must be monotonically increasing.

Second input (column) breakpoint set

The vector of values containing possible block input values for the second input variable. The second input vector must be monotonically increasing.

Make initial table an input

Selecting this check box forces the Adaptive Lookup Table (2D Stair-Fit) block to ignore the Table data (initial) parameter, and creates a new input port Tin. Use this port to input the table data.

Table data (initial)

The initial table output values. This 2-by-2 matrix must be of size (n-1)-by-(m-1), where n is the number of first input breakpoints and m is the number of second input breakpoints.

Table numbering data

Number values assigned to cells. This matrix must be the same size as the table data matrix, and each value must be unique.

Choose Sample mean or Sample mean with forgetting. Sample mean averages all the values received within a cell. Sample mean with forgetting gives more weight to the new data. How much weight is determined by the Adaptation gain parameter. For more information, see Selecting an Adaptation Method.

A number from 0 to 1 that regulates the weight given to new data during the adaptation. A 0 means short memory (last data becomes the table value), and 1 means long memory (average all data received in a cell).

Selecting this check box creates an additional output port Tout for the adapted table.

Selecting this check box creates an additional input port Enable that enables, disables, or resets the adaptive lookup table. A signal value of 0 applied to the port disables the adaptation, and signal value of 1 enables the adaptation. Setting the signal value to 2 resets the table values to the initial table data.

Selecting this check box creates an additional input port Lock that provides the means for updating only specified cells during a simulation run. A signal value of 0 unlocks the specified cells and signal value of 1 locks the specified cells.

Action for out-of-range input

Ignore or Adapt by extrapolating beyond the extreme breakpoints.