Help me understand the arguments of rcosine () in Matlab

Hi all, i have a problem using the pulse shaping commands in MATLAB i.e. rcosine( ),rcosfir( ),rcosflt( ).

I can't understand the arguments of these commands.

Problem:
We can transmit 'Rs=2W' symbols/sec (Rs is the symbol rate,W is the available bandwidth) with zero ISI if the available bandwidth is W Hz.

But this requires nyquist( ideal) filter ,so we incorporate roll off factor 'r'.Then the above equatio changes to


W=0.5(1+r)Rs Hz.

Now lets suppose we have 'W=4KHz' and r=0 ,the what would be the arguments of the above mentioned commands.

For Ease i'll mention the arguments of these commands


1) rcosine(Fd, Fs)

Fd=digital transfer sampling frequency.Whats this? Is it equal to W(4KHz as mentioned above)or 2*W (according to nyquist sampling theorem )

Fs=filter sampling frequency.What could be the value of this field?