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Finding Consecutive values in array that meet specific Criteria?

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Ryan
Ryan 2015-2-12
回答： Azzi Abdelmalek 2015-2-12
I have a list of values
a = [3 10 7 6 2 3 4 8]
I want to find the longest list of terms where a is greater than a certain threshold. So when a>5. These values would be [10 7 6] for the specific example and I would also like this be the output. Each value is consecutive and greater than the threshold. Although 8 is greater than the threshold, it is not consecutive. I would like to be able to do this without a looping structure if at all possible.

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采纳的回答

Matt J
Matt J 2015-2-12
S=regionprops(a>5,'PIxelIdxList','Area');
[~,idx]=max([S.Area]);
longest = a(S(idx).PixelIdxList)

更多回答（2 个）

Azzi Abdelmalek
Azzi Abdelmalek 2015-2-12
a = [3 10 7 6 2 3 4 8 4 2 7 8 9 10 1 2 7]
idx=[0 a>5 0]
ii=strfind(idx,[0 1]);
jj=strfind(idx,[1 0])-1;
[b1,b2]=max(jj-ii+1);
sequence=a(ii(b2):jj(b2))
Image Analyst
Image Analyst 2015-2-12
If you have the Image Processing Toolbox, it's just basically 2 or 3 lines of code : a call to bwlabel and one call to regionprops:
% Check that user has the Image Processing Toolbox installed.
hasIPT = license('test', 'image_toolbox');
if ~hasIPT
% User does not have the toolbox installed.
message = sprintf('Sorry, but you do not seem to have the Image Processing Toolbox.\nDo you want to try to continue anyway?');
reply = questdlg(message, 'Toolbox missing', 'Yes', 'No', 'Yes');
if strcmpi(reply, 'No')
% User said No, so exit.
return;
end
end
a = [3 10 7 6 2 3 4 8]
% Threshold greater than 5 and label.
labeled = bwlabel(a > 5)
measurements = regionprops(labeled, a, 'area', 'PixelValues')
% Get all the areas (lengths of runs above threshold).
allAreas = [measurements.Area]
% Sort them in descending order
[sortedAreas, sortIndices] = sort(allAreas, 'Descend')
% Get the values of the data with the longest run (largest area).
fprintf('The values of the longest run are: ');
valuesOfLongest = measurements(sortIndices(1)).PixelValues;
fprintf('%d ', valuesOfLongest);
fprintf('\n');
In the command window, you'll see the results:
a =
3 10 7 6 2 3 4 8
labeled =
0 1 1 1 0 0 0 2
measurements =
2x1 struct array with fields:
Area
PixelValues
allAreas =
3 1
sortedAreas =
3 1
sortIndices =
1 2
The values of the longest run are: 10 7 6
If you don't follow that, let me know.

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