Fixed-Point Blockset

Summary: Using the Lookup Table Functions

The following summarizes how to use the lookup table approximation functions:

1. Define
1. The ideal function to be approximated
2. The range, xmin to xmax, over which to find X and Y data
3. The fixed-point implementation: data type, scaling, and rounding method
4. The maximum acceptable error, the maximum number of points, and the spacing
2. Run the fixpt_look1_func_approx function to generate X and Y data.
3. Use the fixpt_look1_func_plot function to plot the function and error between the ideal and approximated function using the selected X and Y data, and to calculate the error and the number of points used.
4. Vary input criteria, such as errmax, nptsmax and spacing, to produce sets of X and Y data that generate functions with varying worst-case error, number of points required, and spacing.
5. Compare results of the number of points required and maximum absolute error from various runs to choose the best set of X and Y data.

Comparing the Examples

Effect of Spacing on Speed, Error, and Memory Usage