Kmeans clustering in YUV image space

Hi all.

I have a problm in kmeans clustering using matlab.when I apply kmeans function in my image I get following error

Warning:Emty Cluster created at iteration 1.

Warning:Emty Cluster created at iteration 2.

Warning:Emty Cluster created at iteration 3.

Warning:Emty Cluster created at iteration 4.

I am using it becasue I am reducing colors of image and want to get the most representative colors of image. How can I solve this error.y code is under

NoColors=40;

K=40;
[Rows Cols NumberofColors ]=size(image);
s_img=size(image);
inputImg=zeros((s_img(1)*s_img(2)),3);
inputImg(:,2)=U(:);
 inputImg(:,3)=V(:);
 inputImg=double(inputImg);
 %Kmeans starting
 [idx C]=kmeans(inputImg,NoColors,'EmptyAction','singleton');
% %Kmeans Completed
palette=round(C);
% %Color Mapping
idx=uint8(idx);
 outImg=zeros(s_img(1),s_img(2),3);
 temp=reshape(idx,[s_img(1) s_img(2)]);
 for i=1:1:s_img(1)
   for j=1:1:s_img(2)
         outImg(i,j,:)=palette(temp(i,j),:);
     end
 end
Remember image is in YUV space and just want to quantize the color of UV image.
Thannks

Answer 1

[Thorsten]

 [idx C]=kmeans([U(:) V(:)],NoColors,'EmptyAction','singleton');

Answer 2

[Elad]

perhaps this would help: http://imageprocessingblog.com/color-reduction-using-k-means-clustering/