kmeans appear to miss obvious clusters
1 view (last 30 days)
I am struggling to get kmeans to identify what appear to be fairly distinct clusters in my data. I've walked through the documentation and examples but can't improve over the images shown below (raw data plotted first followed by the kmeans result, data also attached). I've tried the different distance and start options without much success. Even giving seed values doesn't improve the clustering. Does anyone have any other suggestions I could try? My goal is to end up with each data point falling into one of 3 clusters. My last command was:
[cidx3,cmeans2] = kmeans(X,3,'dist','cosine','display','iter','Start',seeds);
[0.018660 872 17.59;
0.002100 1140 18.88;
0.004652 1187 34.82]
Ilya on 7 Jul 2017
Do this (assuming there are no nan's in X):
[cidx3,cmeans2] = kmeans(zscore(X),3,'dist','cosine','display','iter');
Did it get better? If yes, look at your data again and think about what went wrong in your previous attempts. Look at the scales. Plot it using real scales 1:1. Think about how the cosine distance works when the data are shifted far away from zero.
More Answers (1)
Image Analyst on 7 Jul 2017
You might want to normalize your data.
I don't think it's good to try to find clusters when one parameter goes from 0 to 1500 and another goes from 0 to 0.05 !!!
With these ranges, your data is basically in a skinny flat sheet, not a 3-D widely spread out space.