How to script this: returns all the x coordinates that distance between X and Y are bigger than r distant ?

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Peyman Obeidy 2017-6-2

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https://ww2.mathworks.cn/matlabcentral/answers/342990-how-to-script-this-returns-all-the-x-coordinates-that-distance-between-x-and-y-are-bigger-than-r-di

评论： Peyman Obeidy 2017-6-3

I put together this, which is returning the y coordinates that are having greater distance than 2 e.g.

%
rng(1); % For reproducibility
X = randn(50,2);%GreenPeak
Y = randn(4,2);%RedPeak;
%imshow(Ifinalb); hold on ;
h = zeros(3,1);
figure;
h(1) = plot(X(:,1),X(:,2),'bx');
hold on;
h(2) = plot(Y(:,1),Y(:,2),'rs','MarkerSize',10);
%title('Heterogenous Data')
%%-----------------------
%Choose weights for each dimension, and specify the chi-square distance function. The distance function must:
%Take as input arguments one row of X, e.g., x, and the matrix Z.
%Compare x to each row of Z.
%Return a vector D of length $n_z$, where $n_z$ is the number of rows of Z.
%Each element of D is the distance between the observation corresponding to x and the observations corresponding to each row of Z
hold on
w = [2; 2];
chiSqrDist = @(x,Z)sqrt((bsxfun(@minus,x,Z).^2)*w);
%Find the indices of the three nearest observations in X to each
%observation in Y.k=3
k = 1;
[Idx,D] = knnsearch(X,Y,'Distance',chiSqrDist,'k',k);
%[Idx,D]= knnsearch(X,Y,'dist','cityblock','k',k);
TableDisInd(:,1)=Idx(:,1);
TableDisInd(:,2)=D(:,1);
Indx2=find(TableDisInd(:,1)>=2);
TableDisInd2=TableDisInd(Indx2,:);

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KSSV 2017-6-2

In that case....pick the first index from Idx and remove it from X....

Peyman Obeidy 2017-6-2

:) How to do this?

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Answer 1

KSSV 2017-6-2

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/342990-how-to-script-this-returns-all-the-x-coordinates-that-distance-between-x-and-y-are-bigger-than-r-di#answer_269334

在 MATLAB Online 中打开

X1 = X ;   % this your X coordinates, in which you want to remove one point 
X1(Idx(1),:) = [] ;   % remove the first index from Idx

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Peyman Obeidy 2017-6-2

Thank you, greatly appreciate your help.

Peyman Obeidy 2017-6-3

在 MATLAB Online 中打开

with a bit of modification here is the code;

w = [2; 2];
chiSqrDist = @(x,Z)sqrt((bsxfun(@minus,x,Z).^2)*w);
%Find the indices of the three nearest observations in X to each
%observation in Y.k=3
k = 1;
[Idx,D] = knnsearch(X,Y,'Distance',chiSqrDist,'k',k);
%[Idx,D]= knnsearch(X,Y,'dist','cityblock','k',k);
TableDisInd(:,1)=Idx(:,1);
TableDisInd(:,2)=D(:,1);
% you are introduceing what needs to be delete, so if you want everything
% bigger than 4 you need to delet everything smaller than 4
Indx2=find(TableDisInd(:,2)<4);
TableDisInd2=TableDisInd(Indx2,:);
%use the first col of "TableDisInd2" to find the index in X table
Idx2=TableDisInd2(:,1);
X1 = X ;   % this your X coordinates, in which you want to remove one point 
%X1(Indx2(:,1),:) = [] ;   % remove the first index from Idx
X1(Idx2(:,1),:) = [] ;   % remove all the close distances from  X list