Using grpdelay sampling frequency

Hi,

I am new to DSP and currently following an example for all pass filters. in the following code, I noticed an error occurs calculating the iirgrpdelay when I change the elliptical order to a larger value (ie N = 16), however this issue is fixed when the sampling frequency in grpdelay (I am assuming that 2 in the grpdelay is the sampling frequency) is changed to a higher value. Thus, I don't seem to understand the relationship there and how the sampling frequency affects the values of g to be less abrupt(ie, when sampling frequency is 2, and the elliptical order is increased to 16, the vector g would contain a sudden large decrease in value at around point 192-193):

close all

clear all

[be,ae] = ellip(4,1,40,0.2);

fvtool (be, ae);

f = 0:0.001:0.2;

g = grpdelay(be, ae, f, 2);

g1 = max(g)-g;

[b,a,tau] = iirgrpdelay(8, f, [0 0.2], g1); % Phase compensator

gd = grpdelay(b,a,f,2);

figure plot(f, g); hold on; plot(f, g+gd, 'r'); hold off;