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Approximate four-dimensional function using specified lookup method

**Library:**Simscape / Foundation Library / Physical Signals / Lookup Tables

The PS Lookup Table (4D) block computes an
approximation to some function `f=f(x1,x2,x3,x4)`

given the
`x1`

, `x2`

, `x3`

,
`x4`

, `f`

data points. The four inputs and the
output are physical signals.

You define the lookup table by specifying the **Table grid vector 1**
parameter (vector of data points along the first axis), the **Table grid vector
2** parameter (vector of data points along the second axis), the
**Table grid vector 3** parameter (vector of data points along the
third axis), the **Table grid vector 4** parameter (vector of data
points along the fourth axis), and the **4D array of table values**
parameter (array of output values).

The `x1`

, `x2`

, `x3`

, and
`x4`

data vectors must be strictly monotonic, either increasing or
decreasing. The array size of the tabulated function values must match the dimensions
defined by the input vectors. That is, if the four input vectors have sizes
1-by-`m`

, 1-by-`n`

, 1-by-`p`

, and
1-by-`q`

, respectively, supply an
`m`

-by-`n`

-by-`p`

-by-`q`

array of output values.

The block generates output based on the input grid lookup using the selected interpolation and extrapolation methods. You have a choice of two interpolation methods and two extrapolation methods. You also have an option for the block to issue an error if any of the input signal values is outside the respective table grid vector range.