Fixed-Point Blockset

Example 4: Using nptsmax with Even Spacing

The next example shows how to create a lookup table that has evenly space breakpoints and minimizes the worst case error for a specified maximum number of points. To try the example, you must first enter the parameter values given in the section Setting Function Parameters for the Lookup Table, if you have not already done so in this MATLAB session.

Next, at the MATLAB prompt type

• spacing='even';
  [xdata ydata errworst]= fixpt_look1_func_approx(funcstr,...
  xmin,xmax,xdt,xscale,ydt,yscale,rndmeth,[],nptsmax,spacing);
  

The result requires 21 evenly spaced points to achieve a maximum absolute error of 2^-10.2209.

To plot the lookup table along with the errors, type

• fixpt_look1_func_plot(xdata,ydata,funcstr,xmin,xmax,xdt,...
  xscale,ydt,yscale,rndmeth);
  
  
  

Example 3: Using errmax with Even Spacing

Example 5: Using errmax with Power of Two Spacing