# How do I identify close matched regions from this vector?

4 views (last 30 days)
Faraz on 20 Mar 2014
Commented: Faraz on 28 Mar 2014
Hello,
I have this 1D vector: posted in Pastebin .
Just by looking at it I can tell that I have 4 different regions, 0 to 122 then 375 to 563, 1145 to 1292 and 1697 to 2242. This is based on how much one region "jumps" to another.
Is there any way in Matlab in which I can identify these regions from this vector?
Thank you

Star Strider on 20 Mar 2014
Edited: Star Strider on 21 Mar 2014
There may be more efficient ways to do what you want, but this at least seems to work:
v = [ 9 18 21 58 59 60 63 66 69 70 72 74 ...
dv = diff([0 v]); % Create difference vector
dvs = [mean(dv) std(dv)]; % Determine mean & std
dvd = [0 find(dv > 1.96*dvs(2)+dvs(1)) length(v)]; % Use ‘dvs’ to detect discontinuities & create index reference vector
for k1 = 1:length(dvd)-1
vs{k1} = v(dvd(k1)+1:dvd(k1+1)-1); % Create cell array of regions-of-interest
vi{k1} = [dvd(k1)+1 dvd(k1+1)-1]; % Create reference array of start-end indices for ‘vs’ regions
end
The v vector are your data, the vi cell array contains the beginning and end indices of your segments-of-interest, and the vs cell array contains the data in your segments-of-interest. A cell array is necessary for vs because the vectors are of different lengths. (See the documentation for cell2mat to convert cell arrays back into doubles.)
Faraz on 28 Mar 2014
@StarStrider and @ImageAnalyst
Thanks a lot, you guys were very helpful in your explanations. I believe I have a firm grip of the solution now.
Duly noted and agreed with the email thing, will post here from now on.

Image Analyst on 20 Mar 2014
What do you mean by identify? It seems like you just did when you described the range of values that each takes. Do you want the indexes of each class? Do you want those intensity ranges specified automatically depending on each vector, like as if you use kmeans() or something? You (or someone) tagged it with image Processing so do you want to do connected components analysis (useful if some regions in an intensity range are not touching each other)?
Image Analyst on 26 Mar 2014
You've been very helpful. It can get confusing when people don't give the whole context so we don't know what the big picture is. Even more frustrating is when you know the big picture but people are dead set on going down a path that you know is a dead end , and when you suggest a workable approach they continue to try their dead end approach.