To map two inputs to an output, see FixPt Look-Up Table (2D).

You define the table by specifying the Vector of input values parameter as a 1 × n vector and the Vector of output values parameter as a 1 × n vector. The block generates output based on the input values using one of these methods selected from the Method parameter list:

• Interpolation-Extrapolation -- This is the default method; it performs linear interpolation and extrapolation of the inputs.
• If a value matches the block's input, the output is the corresponding element in the output vector. 
• If no value matches the block's input, then the block performs linear interpolation between the two appropriate elements of the table to determine an output value. If the block input is less than the first or greater than the last input vector element, then the block extrapolates using the first two or last two points.
• Interpolation-Use End Values -- This method performs linear interpolation as described above but does not extrapolate outside the end points of the input vector. Instead, the end-point values are used. 
• Use Input Nearest -- This method does not interpolate or extrapolate. Instead, the element in x nearest the current input is found. The corresponding element in y is then used as the output. 
• Use Input Below -- This method does not interpolate or extrapolate. Instead, the element in x nearest and below the current input is found. The corresponding element in y is then used as the output. If there is no element in x below the current input, then the nearest element is found. 
• Use Input Above -- This method does not interpolate or extrapolate. Instead, the element in x nearest and above the current input is found. The corresponding element in y is then used as the output. If there is no element in x above the current input, then the nearest element is found.

Note:
To avoid parameter saturation errors, the automatic scaling script autofixexp employs a special rule for the FixPt Look-Up Table block. autofixexp  modifies the scaling by using the output look-up values in addition to the logged minimum and maximum simulation values. This prevents the data from being saturated to different values. For this block, the look-up values are given by the Vector of output values parameter (the YDataPoints variable). 

Parameters and Dialog Box

Vector of input values

The vector of input values must be the same size as the output vector and strictly monotonically increasing.

Vector of output values

The vector of output values must be the same size as the input vector.

Method

Look-up method.

Output data type

Any data type supported by the Fixed-Point Blockset.

Output scaling

Radix point-only or slope/bias scaling. These scaling modes are only available for generalized fixed-point data types.

Lock output scaling

If checked, Output scaling is locked. This feature is only available for generalized fixed-point output.

Round toward

Rounding mode for the fixed-point output.

Saturate to max or min when overflows occur

If checked, fixed-point overflows saturate. Otherwise, they wrap.

Override with doubles

If checked, the Output data type is overridden with doubles.

Log minimums and maximums

If checked, minimum and maximum simulation values are logged to the workspace.

Conversions

The Vector of input values parameter is converted from doubles to the input data type. The Vector of output values parameter is converted from doubles to the output data type. Both conversion are performed offline using round-to-nearest and saturation. Refer to "Parameter Conversions" in the manual for more information about parameter conversions. 

Characteristics

Input Port(s)	Any data type supported by the blockset
Output Port	Any data type supported by the blockset
Direct Feedthrough	Yes
Sample Time	Inherited
Scalar Expansion	No
States	0
Vectorized	Yes

Example

This example illustrates the look-up methods supported by the FixPt Look-Up Table block.Suppose you have a vector of input values given by [-5:5] and a vector of output values given by sinh([-5:5]). Using the model shown below,

these results were generated.

Look-Up Method	Input	Output	Comment
Interpolation-Extrapolation	1.4	2.153	N/A
	5.2	83.59	N/A
Interpolation-Use End Values	1.4	2.153	N/A
	5.2	74.2	The value for sinh(5.0) was used.
Use Input Nearest	1.4	1.175	The value for sinh(1.0) was used.
Use Input Below	1.4	1.175	The value for sinh(1.0) was used.
	-5.2	-74.2	The value for sinh(-5.0) was used.
Use Input Above	1.4	3.627	The value for sinh(2.0) was used.
	5.2	74.2	The value for sinh(5.0) was used.