aguirreg

function mseqbur = mseqburmeth(a)
% mseqbur = mseqburmeth
% 
% This function creates a pseudomsequence with 9 event levels using the way
% suggested by Buracas from Buracas and Boyton 2002.
%
% This method is to:
% 1. Take a binary [0 1] msequence of the correct length.
% 2. Cyclically shift the sequence (no specific shift, try to see what
%        works)
% 3. Multiply the sequence by 2.
% 4. Add the original sequence.
% 5. Multiply a binary [0 1] msequence by 4.
% 6. Shift the [0 4] sequence cyclically.
% 7. Add the [0 1 2 3] sequence to the shifted [0 4] sequence.
% 8. View and test sequence.
%
%
% Input:
% a : shift of [0 2] mseq
% b : negative shift of [0 4] mseq
%
%
% Buracas GT, Boyton GM (2002). "Efficient Design of Event-Related fMRI
% Experiments Using M-Sequences" NeuroImage 16, 801-813.
%
% The msequence generator called in this function is subject to copyright.
%
% Contact:
% Wesley Kerr
% wesleytk@sas.upenn.edu
 
baseseq=mseq(3,6);
nlength=length(baseseq);
 
for i=1:nlength
    if baseseq(i)==-1
        baseseq(i)=2;
    end
end
 
base3=baseseq*3;
base3b=zeros(nlength,1);
burseq=zeros(nlength,1);
 
for i=1:nlength
    shift3=mod(i+a,nlength)+1;
    base3b(i)=base3(shift3);
    burseq(i)=baseseq(i)+base3b(i);
end
clear baseseq i base3 base3b shift3 nlength
 
mseqbur=burseq;
clear burseq