Repeated values (multiple data points at the same location).

Hi all,

I have an array of data and in the first column there are some repeated values (multiple data points at the same location). With those repeated values I'd like to average the associated data in column 2.

Example array: [1 3.1; 2 4.5; 3 5.7; 4 8.2; 4 5.2;]

I'd like to create a new array that looks like this: [1 3.1; 2 4.5; 3 5.7; 4 6.7;]

Thanks for any help.

-K

Answer 1

[Star Strider]

The accumarray function will do this if you ask it nicely:

ExArray = [1 3.1; 2 4.5; 3 5.7; 4 8.2; 4 5.2;];

[UExA, ia, ic] = unique(ExArray(:,1));

Out = [ExArray(ia,1) accumarray(ic, ExArray(:,2), [], @mean)]

Out =
            1          3.1
            2          4.5
            3          5.7
            4          6.7

[Kyriakos Kokolakis]

Thanks alot for your answer. I got this error: Error using cell/unique (line 86) Input A must be a cell array of strings.

[Star Strider]

You didn’t say you had a cell array. That makes a significant difference in the code.

I still don’t know what your data look like, so see if this works:

ExCellArray = {[1 3.1; 2 4.5; 3 5.7; 4 8.2; 4 5.2]};
ExArray = cell2mat(ExCellArray);

[UExA, ia, ic] = unique(ExArray(:,1));

Out = [ExArray(ia,1) accumarray(ic, ExArray(:,2), [], @mean)]

It’s the same as before, adding the cell2mat call.

[Kyriakos Kokolakis]

Thank you very much!

[Star Strider]

My pleasure!

Your problem was fun to solve!