How to apply RBF kernel function in k means cluster? Here is the code

This is the code

grayImage= imread('CYST RENAL -87.jpg');

g = rgb2gray(grayImage);

g = double(g);

sigma = 0.4;

[n,d] = size(g);

nms = sum(g'.^2);

Ks = exp(-(nms'*ones(1,n) -ones(n,1)*nms + 2*g*g')/(2*sigma^2));

[m n]=kmeans(Ks,3);

m=reshape(m,size(Ks,1),size(Ks,2));

B=labeloverlay(Ks,m);

figure;

imshow(B);

I am unable to solve this error. Plshelp me to solve this error and explain how to apply kernel functions in k means clusetering

Error using reshape Number of elements must not change. Use [] as one of the size inputs to automatically calculate the appropriate size for that dimension.

Answer 1

[Pratyush Roy]

Hi,

For data in matrix form, the kmeans algorithm assumes that individual rows are the data instances. So when we apply kmeans on an N*N matrix, it returns a N*1 index array instead of an N^2*1 index array.

As a workaround, we can consider

1. Converting the Ks matrix into a column vector Ks_vec with the same number of elements as Ks.
2. Applying kmeans on Ks_vec to obtain the labels for each element,
3. Reshape it back to the shape of Ks.

grayImage= imread('CYST RENAL -87.jpg');
g = rgb2gray(grayImage);
g = double(g);
sigma = 0.4;
[n,d] = size(g);
nms = sum(g'.^2);
Ks = exp(-(nms'*ones(1,n) -ones(n,1)*nms + 2*g*g')/(2*sigma^2));
Ks_vec = reshape(Ks,[size(Ks,1)*size(Ks,2),1]);
[m n]=kmeans(Ks_vec,3);
m=reshape(m,size(Ks,1),size(Ks,2));
B=labeloverlay(Ks,m);
figure;
imshow(B);

Hope this helps!

[MINO GEORGE]

Hi, thank you for responding. Here is the image after applying the code the code.Sometthing went wrong

This is my original image

Pls help me to segment the roi