Fixed-Point Blockset

Example 3: Using errmax with Even Spacing

The next example shows how to create a lookup table that has evenly spaced breakpoints and a specified worst case error. 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,errmax,[],spacing);
  

You can find the number of points in the lookup table by typing length(xdata).

• ans =
      20
  

To plot the lookup table along with the errors, type

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

This produces the following plots.

Example 2: Using nptsmax with Unrestricted Spacing

Example 4: Using nptsmax with Even Spacing