Find duplicate entries and average associated values

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Chris
Chris 2014-6-5
回答： Kalpana Patel 2021-4-19
Hi all,
I have a 180 x 2 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. Any help with this would be appreciated greatly.
Example array: [1 10; 2 20; 3 30; 4 40; 4 50; 4 60; 5 70; 6 80; 7 90; 7 100; 8 110]
I'd like to create a new array that looks like this: [1 10; 2 20; 3 30; 4 50; 5 70; 6 80; 7 95; 7 100; 8 110]
Thanks a ton for any help.
-Chris

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采纳的回答

José-Luis
José-Luis 2014-6-5
array = [1 10; 2 20; 3 30; 4 40; 4 50; 4 60; 5 70; 6 80; 7 90; 7 100; 8 110];
[C,ia,idx] = unique(array(:,1),'stable');
val = accumarray(idx,array(:,2),[],@mean);
your_mat = [C val]

更多回答（5 个）

Cedric
Cedric 2014-6-5
编辑：Cedric 2014-6-5
If elements from the first column are "continuous" positive integers, here is a way to go:
>> data = [1 10; 2 20; 3 30; 4 40; 4 50; 4 60; 5 70; 6 80; 7 90; 7 100; 8 110] ;
>> newData = [unique( data(:,1) ), ...
accumarray( data(:,1), data(:,2), [], @mean )]
newData =
1 10
2 20
3 30
4 50
5 70
6 80
7 95
8 110
If you don't have "continuity" (i.e. there are gaps), here is a more general solution (I removed row 5 70 from previous data):
>> data = [1 10; 2 20; 3 30; 4 40; 4 50; 4 60; 6 80; 7 90; 7 100; 8 110] ;
>> uc1 = unique( data(:,1) ) ;
>> mc2 = accumarray( data(:,1), data(:,2), [], @mean ) ;
>> newData = [uc1, mc2(uc1)]
newData =
1 10
2 20
3 30
4 50
6 80
7 95
8 110
derGerät
derGerät 2015-10-29
Hey all, I have kind of the same problem but my data ar not in one array but two arrays. Is it possible to adept this solution to make it work with two arrays?
Sorry if thats a stupid question but I'm a beginner...
Chris
Chris 2014-6-5
This is great, but the first column elements are actually not integers. They are continuous, but they have precision up to three decimal points.
Thanks for the quick reply.
Chris
Chris 2014-6-5
Incredible, thanks so much José-Luis and Cedric. I've just learned so many new things from these few lines of code.
  2 个评论
Cedric
Cedric 2014-6-5
My pleasure, note that I assumed integers because, as far as I am concerned, it is rarely appropriate to use UNIQUE on floating points, for the same reason it is rarely appropriate to test equality between floats.

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Kalpana Patel
Kalpana Patel 2021-4-19
how to filter the repeated datain a data series maintaining the length. I have two column, one is for latitude and second is for ion density, with the use of unique code length is maot maintain. reason i know. so just want single latitude valua and data corresponding to it. total data values are 4892. pls help..

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