fixpt_evenspace_cleanup - Modify breakpoints of lookup table to have even spacing

Syntax

Description

xdata_modified = fixpt_evenspace_cleanup(xdata,xdt,xscale) modifies breakpoints of a lookup table to have even spacing after quantization. By adjusting breakpoints to have even spacing after quantization, Simulink Coder generated code can exclude breakpoints from memory.

xdata is the breakpoint vector of a lookup table to make evenly spaced, such as 0:0.005:1. xdt is the data type of the breakpoints, such as sfix(16). xscale is the scaling of the breakpoints, such as 2^-12. Using these three inputs, fixpt_evenspace_cleanup returns the modified breakpoints in xdata_modified.

This function works only with nontunable data and considers data to have even spacing relative to the scaling slope. For example, the breakpoint vector [0 2 5], which has spacing value 2 and 3, appears to have uneven spacing. However, the difference between the maximum spacing 3 and the minimum spacing 2 equals 1. If the scaling slope is 1 or greater, a spacing variation of 1 represents a 1-bit change or less. In this case, the fixpt_evenspace_cleanup function considers a spacing variation of 1 bit or less to be even.

Modifications to breakpoints can change the numerical behavior of a lookup table. To check for changes, test the model using simulation, rapid prototyping, or other appropriate methods.

Examples

Modify breakpoints of a lookup table to have even spacing after quantization:

xdata = 0:0.005:1;
xdt = sfix(16);
xscale = 2^-12;
xdata_modified = fixpt_evenspace_cleanup(xdata,xdt,xscale)

See Also

fixdt | fixpt_interp1 | fixpt_look1_func_approx | fixpt_look1_func_plot | sfix | ufix

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