simulate k nearest neighbourhood

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Ahsen Feyza Dogan 2019-7-4

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https://ww2.mathworks.cn/matlabcentral/answers/470190-simulate-k-nearest-neighbourhood

回答： Ahsen Feyza Dogan 2019-7-5

Hi,

I want to simulate knn. When I add a new point on graph where other data points are on, it can predict class of it, but I don't have any idea about what to do after I upload a data set.

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KSSV 2019-7-4

What exactly you want to do?

Ahsen Feyza Dogan 2019-7-4

编辑：KSSV 2019-7-4

I want to determine knn determine random point that I click on to determine which group like in this video but I tried its code does not working https://youtu.be/0pZQ-PAGRj8

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采纳的回答

KSSV 2019-7-4

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https://ww2.mathworks.cn/matlabcentral/answers/470190-simulate-k-nearest-neighbourhood#answer_381919

在 MATLAB Online 中打开

Play with this:

x = rand(500,1) ; y = rand(500,1) ; 
l = kmeans([x y],4) ; 
figure
hold on
scatter(x,y,50,l,'o','filled')
N = 10 ; 
for i = 1:100
    % pick any point 
    [ptx,pty] = getpts() ; 
    idx = knnsearch([x y],[ptx pty],'k',N)' ;
    li = mean(l(idx)) ;
    text(ptx,pty,num2str(li))
    plot(ptx,pty,'*r')
    plot([ptx*ones(N,1) x(idx)]',[pty*ones(N,1) y(idx)]','r')
end

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KSSV 2019-7-5

The result is correct in given code......code is showing up different groups/ labels. Attach your data and code to rectify the error.

KSSV 2019-7-5

Why/how for loop is a trianing? For knnsearch there wont be any training. It gets the specififed number of nearest neighbors by calculating distances.

That line of plot is to show up lines joining the picked point and it's neighbors.

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