tomwalters@0: % method of class @signal
tomwalters@0: % 
tomwalters@0: %   INPUT VALUES:
tomwalters@0: %  
tomwalters@0: %   RETURN VALUE:
tomwalters@0: %
tomwalters@0: % 
bleeck@3: % This external file is included as part of the 'aim-mat' distribution package
bleeck@3: % (c) 2011, University of Southampton
bleeck@3: % Maintained by Stefan Bleeck (bleeck@gmail.com)
bleeck@3: % download of current version is on the soundsoftware site: 
bleeck@3: % http://code.soundsoftware.ac.uk/projects/aimmat
bleeck@3: % documentation and everything is on http://www.acousticscale.org
bleeck@3: 
tomwalters@0: 
tomwalters@0: function sig=secondderivation(sig)
tomwalters@0: % calculates the second derivation by calculation of the differences
tomwalters@0: 
tomwalters@0: 
tomwalters@0: val=getvalues(sig);
tomwalters@0: 
tomwalters@0: nr=length(val);
tomwalters@0: 
tomwalters@0: 
tomwalters@0: nval=val;
tomwalters@0: nval(1)=0;
tomwalters@0: nval(2)=0;
tomwalters@0: for i=3:nr
tomwalters@0: 
tomwalters@0:     if i==370
tomwalters@0:         a=0;
tomwalters@0:     end
tomwalters@0:     nval(i)=(val(i-2)-2*val(i-1)+val(i))/2;
tomwalters@0: end
tomwalters@0: 
tomwalters@0: sig=setvalues(sig,nval);