how to find closest values in array)

I want to find closest numbers in array as shown in example a=[4 7 8 9 10 11 20 23 26 27 28 29 30 60] output first group 7 8 9 10 11 second group 26 27 28 29 30

[Stephen23]

How do you define groups membership? (i.e. what are the distinguishing features of values that belong to the same group?) Do you know how many groups there are in the array, or do you need to automatically detect how many groups there are? How many dimensions does the array have?

[mona]

I need to automatically detect how many groups there are , each group membership is array and has values that difference between each number and next number is one. array is one dimension

[Alex L]

Is your array always going to be sorted? To refine your question: You are looking for groups of integers in your array that have an absolute difference of 1 to either the preceding or the following integer in the array?

Answer 1

[Image Analyst]

If you have the Image Processing Toolbox, you can use bwlabel to give an "ID number" to each group that has the minimum spacing. Then you can extract each of those labeled groups one at a time and put into a cell array.

a=[4 7 8 9 10 11 20 23 26 27 28 29 30 60] % Original, easy case: separate groups
% a=[4 7 8 9 10 11 12 25 26 27 28 29 30 60] % Tricky test case: groups adjacent/touching
% a=[6 7 8 9 10 11 12 25 26 27 28 29 30 31] % Tricky test case: groups touch each other and ends
diffs = diff(a)
minSpacing = min(diffs)
binaryLabels = diffs == minSpacing
% Label the groups
labeledgroups = bwlabel(binaryLabels)
% Extract each group
for k = 1 : max(labeledgroups)
  thisGroupsIndexes = find(labeledgroups == k);
  % Tack one more.
  thisGroupsIndexes = [thisGroupsIndexes, thisGroupsIndexes(end)+1]
  % Extract these elements from the original "a" vector
  result{k} = a(thisGroupsIndexes)
end