How to combining repeating groups of elements of an array while preserving order?

I am having trouble combining repeated elements of my Matlab "data" variable. I can easily combine the values using unique and sort.

[sorted,idx] = sort(data);
[~,ij] = unique(sorted,'first');
Indx = (sort(idx(ij)));

However, by doing this I am combining ALL repeated values. What I really want to do is combine only groups of repeating elements. For example take this:

data = [1;1;1;2;2;2;3;3;3;4;4;4;4;4;3;3;2;2;2;2;1;1;1;1;4;4;4;4;]

Combine duplicate groups of elements:

data = [1;2;3;4;3;2;1;4;]

I need to combine the groups of repeating elements wile still preserving the order. It would also be helpful to return the index because I need to average data in another variable based on the index of combination.

For example:

data  = [1;1;1;2;2;2;3;3;3;4;4;4;4;4;3;3;2;2;2;2;1;1;1;1;4;4;4;4;]
data2 = [7;2;4;5;3;4;6;8;5;3;5;7;4;2;4;6;8;4;3;6;7;8;4;2;9;3;2;0;]

dataCombined = [1;     2;  3;    4;   3;  2;     1;     4;   ]
data2average = [4.33;  4;  6.33  4.2  5;  5.25;  5.25;  3.5; ]

Can anyone give suggestions?

Answer 1

[the cyclist]

data  = [1;1;1;2;2;2;3;3;3;4;4;4;4;4;3;3;2;2;2;2;1;1;1;1;4;4;4;4;];
data2 = [7;2;4;5;3;4;6;8;5;3;5;7;4;2;4;6;8;4;3;6;7;8;4;2;9;3;2;0;];

groupIndex = cumsum(abs(diff([nan;data]))~=0);

dataCombined = accumarray(groupIndex,data,[],@mean)
data2average = accumarray(groupIndex,data2,[],@mean)