converting Matlab's

Hi,
I'm trying 2 realize the function "butter" as iin matlab, using scilab.
So instead of
   [a, b]=butter(ord,[int1* 2/Freq int2*2/Freq]);
I write the following:
    hz=iir(ord,'lp', 'butt', [int1/Freq int2/Freq], [0 0]);
    a=coeff(denom(hz));a=a($:-1:1);
    b=coeff(numer(hz));b=b($:-1:1);
and I don't get the same results as in matlab.
 
What do I do to get the same results?
p.s. I've user the same 'ord' parameter in both environments.
Also, I suspect the 4th parameter in the call 2 iir function.
Please advice.
Thank you,
Rivka