MATLAB: How to split a vector into unequal sections

diff()indexingsplitting vectors

I know that some similar questions have previously been asked, but I think this problem might be a little unique. For some context, I have this vector V whose values never decrease (is there a word for this?) and whose min (1) and max (5) I always know.:
 V = [1;1;2;2;2;2;3;4;4;5];
I'd like to somehow get the vertices for each "grouping" g (or some other format of distinction such as indexing) of V for like-numbers, i.e.
 g1 = [1;1]
 g2 = [2;2;2;2];
 g3 = 3;
 g4 = [4;4];
 g5 = 5;
What I have right now seems ad hoc and mendable and I am not sure if it will be ideal for large data sets that I intend to apply this toward. I imagine an easier solution would simply obtain indices for each grouping. This is what I've done:
 Vchange = logical(diff(V));
 maxG = 5; % For this case.
 Gidx = 1; % Begin first grouping with minimum.
 G = cell(maxG,1); % Initialize output.
 G{1} = V(1);
 iter = length(Vchange); % Number of iterations.
 for Vidx = 1:iter
     if Vchange(i)        % Vertex has changed;
         Gidx = Gidx + 1; % continue with next vertex.
     end
     G{Gidx} = [G{Gidx},V(i)];
 end

Best Answer

>> V = [1;1;2;2;2;2;3;4;4;5];
>> D = diff(find([1;diff(V)~=0;1]));
>> C = mat2cell(V,D,1);
>> C{:}
ans =
   1
   1
ans =
   2
   2
   2
   2
ans =
   3
ans =
   4
   4
ans =
   5
You can use cell array indexing to access the numeric vectors in C.
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