function shuffled_data_vector=shuffle_columns(original_data_vector)
%called by finding_confidence_for_timeofchangeinSTSD;  shuffles the columns of an array but preserves the structure of each column

shuffled_data_vector=[];
for i=1:size(original_data_vector,2)
    ind=1+round(rand*(size(original_data_vector,2)-1));
    shuffled_data_vector(:,i)=original_data_vector(:,ind);
    original_data_vector(:,ind)=[];
end