Scilab does not have a function to compute the coefficients of a filter using the frequency sampling method. The fsfirlin function comes closest to doing this, however it computes the magnitude of the frequency response of the filter and not the coefficients. The fir2 function in Matlab computes the filter coefficients.
I have been studying filter design using frequency sampling from the following sources:
Rabiner's original paper on frequency sampling filters: http://www.math.unipd.it/~alvise/CS_2008/APPROSSIMAZIONE_2009/MFILES/Remez.pdf
I'm currently writing the code to implement the algorithm in this paper.