Kmeans plot centroid error

Question

Sophie Lis 2018-8-28

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/416463-kmeans-plot-centroid-error

回答： KSSV 2018-8-28

I am trying to cluster my two-dimensional data with k-means clustering, where my data is wv_prop (attached) and am plotting according to the example code provided by matlab. However,I am getting a strange result as seen in the attached figure where there are no points around the 2nd centroid. Anyone know why this might be? It looks like the idx variable contains only 1's, and no 2's.

[idx,C] = kmeans(wv_prop,2);  
figure;
plot(wv_prop(idx==1,1),wv_prop(idx==1,2),'r.','MarkerSize',12)
hold on
plot(wv_prop(idx==2,1),wv_prop(idx==2,2),'b.','MarkerSize',12)
plot(C(:,1),C(:,2),'kx',...
     'MarkerSize',15,'LineWidth',3)
legend('Cluster 1','Cluster 2','Centroids',...
       'Location','NW')
title 'Cluster Assignments and Centroids'
hold off

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

KSSV 2018-8-28

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/416463-kmeans-plot-centroid-error#answer_334328

在 MATLAB Online 中打开

Try removing the outliers:

load('wv_prop.mat')
% Remove outliers
idx =  abs(wv_prop(:,2) - nanmean(wv_prop(:,2))) > 3*nanstd(wv_prop(:,2));
wv_prop(idx,:) = [] ;
[idx,C] = kmeans(wv_prop,2);
figure;
plot(wv_prop(idx==1,1),wv_prop(idx==1,2),'r.','MarkerSize',12)
hold on
plot(wv_prop(idx==2,1),wv_prop(idx==2,2),'b.','MarkerSize',12)
plot(C(:,1),C(:,2),'kx',...
    'MarkerSize',15,'LineWidth',3)
legend('Cluster 1','Cluster 2','Centroids',...
    'Location','NW')
title 'Cluster Assignments and Centroids'
hold off