counting the number of clusters
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I have a list of pair of numbers for example (please see below). In this example, if we look at the first column, the number one (1) repeats 3 times with its pair 54, 106 and 143. Similarly the number 24 repeats two times with its corresponding pair 87 and 288. What i want to do is group all those that repeat to one cluster. In the example listed below there are 12 pairs. I want to group 1 with 54, 106, and 143 and call it as one cluster and do the same thing with any such repeating pairs (number 24 in this example). In the end I will have 12 - 2 = 10 clusters. I would appreciate if some one could help with a matlab code for this.
Thanks,
Sudharsan
[1 54
1 106
1 143
5 90
24 87
64 244
5 202
7 270
24 288
25 176
26 206
27 161]
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Fabio Freschi
2019년 10월 8일
편집: Fabio Freschi
2019년 10월 8일
% unique indices
idx = unique(data(:,1));
% clusters
cluster = arrayfun(@(idx)data(data(:,1) == idx,2),idx,'UniformOutput',false);
Then you can access your clusters with idx(i)and cluster{i}, where i = 1:length(idx)
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Fabio Freschi
2019년 10월 8일
편집: Fabio Freschi
2019년 10월 8일
do you mean the 2 here?
cluster = arrayfun(@(idx)data(data(:,1) == idx,2),idx,'UniformOutput',false);
% ^
% |
I am taking the second column of data to check the values of the cluster.
arrayfun is not simple to understand for newbies, try with
doc arrayfun
Roughly speaking, it basically applys the comparison data(:,1) == idx of the cluster to each value of idx, one element at a time. Then I extract the values of the second column of data using the previous comparison data(data(:,1) == idx,2). 'UniformOutput',false is needed to deal with the output and put every value in a different entry of the cell array cluster
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Image Analyst
2019년 10월 8일
I agree with Stephan and findgroups() -- there are 8 "clusters."
Below I use findgroups() to find the groups, then I store all the rows (actually the values in the second column) into a cell array, where each cell has the second values for that group. Try this:
m = [
1 54
1 106
1 143
5 90
24 87
64 244
5 202
7 270
24 288
25 176
26 206
27 161]
groupIndexes = findgroups(m(:, 1))
% Make clusters as a cell array because every group might have a different number of members.
for k = 1 : max(groupIndexes)
thisGroupRows = groupIndexes == k;
groupValues{k} = m(thisGroupRows, 2);
end
celldisp(groupValues) % Report to the command window
You'll see this:
groupIndexes =
1
1
1
2
4
8
2
3
4
5
6
7
groupValues{1} =
54
106
143
groupValues{2} =
90
202
groupValues{3} =
270
groupValues{4} =
87
288
groupValues{5} =
176
groupValues{6} =
206
groupValues{7} =
161
groupValues{8} =
244
Is that what you want? If you want, you could put those values into the second column of the cell array and have the group value (the column 1 values) in the first column.
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Image Analyst
2019년 10월 12일
Not totally, but try using this:
inBothColumns = m(:, 1) == m(:, 2);
This will give you a logical vector where both numbers in a row are the same.
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