Interpolation (n-D) Using PreLookup (Simulink Reference)

Perform high-performance constant or linear interpolation, mapping N input values to a sampled representation of a function in N variables via output from PreLookup Index Search block

Library

Lookup Tables

Description

The Interpolation (n-D) Using PreLookup block uses the precalculated indices and interval fractions from the PreLookup Index Search block to perform the equivalent operation that the Lookup Table (n-D) performs. This combination of blocks allows multiple Interpolation (n-D) blocks to feed a set of PreLookup Index Search blocks. In models that have many interpolation blocks, simulation performance can be greatly increased.

This block supports two interpolation methods: flat (constant) interval lookup and linear interpolation. These operations can be applied to 1-D, 2-D, 3-D, 4-D and higher dimensioned tables.

You define a set of output values as the Table data parameter. These table values must correspond to the breakpoint data sets that are in the PreLookup Index Search block. The block generates its output by interpolating the table values based on the (index, fraction) pairs fed into the block by each PreLookup Index Search block.

The block generates output based on the input values:

If the inputs match breakpoint parameter values, the output is the table value at the intersection of the row, column, and higher dimensions' breakpoints.
If the inputs do not match row and column parameter values, the block generates output by 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 in each corresponding dimension.

The block can perform interpolation on portion of the table. For more information, see "Lookups: Prelookup and Sub-Table Interpolation Blocks" in the "Block Diagramming Features" section of the "Simulink" section on the Demos pane of the MATLAB Help browser.

Data Type Support

The Interpolation (n-D) Using PreLookup block accepts signals of types double or single, but for any given block, the inputs must all be of the same type. The Table data parameter must be of the same type as the inputs. The output data type is set to the Table data data type.

Parameters and Dialog Box

Number of table dimensions: The number of dimensions that the Table data parameter must have. This determines the number of independent variables for the table and hence the number of inputs to the block (see descriptions for "Explicit Number of dimensions" and "Use one (vector) input port instead of N ports," below).
Table data: The table of output values. The matrix size must match the dimensions defined by the N breakpoint set parameter or by the Explicit number of dimensions parameter when the number of dimensions exceeds four. During block diagram editing, you can leave the Table data field empty, but for running the simulation, you must match the number of dimensions in the Table data parameter to the Number of table dimensions. For information about how to construct multidimensional arrays in MATLAB, see "Multidimensional Arrays in the MATLAB online documentation.
Interpolation method: None (flat) or Linear.
Extrapolation method: None (clip) or Linear.
Action for out of range input: None, Warning, Error.
Number of sub-table selection dimensions: Number of dimensions of the subtable used to compute this block's output. Specify 0 to use the entire table specified by Table data parameter.

Characteristics

Direct Feedthrough
Yes

Sample Time
Inherited from driving blocks

Scalar Expansion
Yes

Zero Crossing
No

Direct Feedthrough	Yes
Sample Time	Inherited from driving blocks
Scalar Expansion	Yes
Zero Crossing	No

Integrator Interval Test