c = c(:);
ii = [true;diff(c)~=0];
i2 = diff([find(ii);numel(ii)+1]);
[a,b,c0] = unique(c(ii),'first'); % in new version of MATLAB:
[~,jj] = sort(b); %
[~,j1] = sort(jj); % [a1,~,c1] = unique(c(ii),'stable');
a1 = a(jj); %
c1 = j1(c0); %
out = [a1,accumarray(c1,i2,[],@mean)];
or with sorting
ii = [true;diff(c)~=0];
i2 = diff([find(ii);numel(ii)+1]);
[a,~,c0] = unique(c(ii));
out1 = [a,accumarray(c0,i2,[],@mean)]
