Different results using buttap and butter

HI, Im having problem with designing IIR filter with buttap and bilinear functions. Filter doesnt match the one designed using butter function. Any ideas where the problem occurs?

fs=30000;
fc=10000;
n=6;
[z,p,k]=buttap(n);
[b,a]=zp2tf(z,p,k);
[be,ae]=lp2lp(b,a,fc);
[numd,dend]=bilinear(be,ae,fs,fc);
[bt,at] = butter(n,fc/(fs/2));
fvtool(numd,dend,bt,at);

[collegebaj]

Ok i fixed it now. I dont know why this [numd,dend]=bilinear(be,ae,fs,fc) doesnt apply prewarping at fc

fs=30000;
fc=10000;
Fc=2*fs*tan((pi/2*fc)/(fs/2))
n=6;
[z,p,k]=buttap(n);
[b,a]=zp2tf(z,p,k);
[be,ae]=lp2lp(b,a,Fc);
[numd,dend]=bilinear(be,ae,fs);
[bt,at] = butter(n,fc/(fs/2));
fvtool(numd,dend,bt,at);

Answer 1

[Sowmiya Sowmiya]

wp=0.3;
ws=0.6;
rp=1;
rs=40;
[N wn]=buttord(wp,ws,rp,rs);
[z,p,k ]=buttap(N)

z =

     []

p = 
  -0.2588 + 0.9659i
  -0.2588 - 0.9659i
  -0.7071 + 0.7071i
  -0.7071 - 0.7071i
  -0.9659 + 0.2588i
  -0.9659 - 0.2588i

k = 1