How can i get KNN classifier for test and training purpose?

I want to study about KNN classifier and i would like to implement it..Where can i get source code..

Answer 1

[Star Strider]

If you do not have the Statistics and Machine Learning Toolbox and with it the knnsearch (link) function, a simple KNN classifier is straightforward to write.

The Code —

V = randi(50,  1, 3);                   % Vector — Create Data
M = randi(50, 15, 3);                   % Matrix — Create Data

dif = bsxfun(@minus, V, M);             % Subtract Vector from Matrix
D2 = sqrt(sum(dif.^2,2));               % Euclidean Distance Metric
[Ds,Ix] = sort(D2,'ascend');            % Sort Ascending
k = 5;                                  % Number Of Neighbours
KNN = M(Ix(1:k),:);                     % K-th Nearest Neighbours

This finds the ‘nearest neighbours’ in ‘M’ to the vector ‘V’. The data in ‘V’ and ‘M’ must have the same column size.

[sam CP]

Is this KNN is an inbuilt function???

[Star Strider]

No. This is code I wrote earlier to illustrate how a k-th nearest neighbour classifier works.

The link I provided in my Answer is to the documentation for the MATLAB function. You must have the Statistics and Machine Learning Toolbox installed to use the knnsearch function.