function y = spectrum(s,fdef)% $Id: spectrum.m 31 2004-07-28 10:46:46Z mairas $y.frequency = [];y.s = s(:).'; % make the signal always a row vectory.fs = [];if isa(fdef,'frequency')  y.frequency = fdef;  y.fs = y.frequency.fs;elseif length(fdef)>1  y.frequency = frequency(fdef);  y.fs = y.frequency.fs;else  y.fs = fdef;  y.frequency = frequency(0,length(y.s),y.fs);endy = class(y,'spectrum');