Distance difference from center

Question

Mehmet Volkan Ozdogan 2019-5-28

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/464446-distance-difference-from-center

编辑： Mehmet Volkan Ozdogan 2019-5-29

采纳的回答： darova

Hi,

I created a cross section by using kmeans function from two different data (indicated by X and * in image),

My aim is to determine the distance difference of two data from center (o) of cross section,

Briefly i try to find the;

Distance between O and X (d1)

Than i need to find the nearest * to X,

Than calculate the distance between O and * (which is nearest X) (d2)

And lastly i need to calculate the difference between (d1) and (d2)

And i want to do this calculations for all X to * in cross-section.

Thank you...

My current code is given below: my points are represented by m,n and o in code...

clc;clear;

x=xlsread('king1.xlsx', 'A:A');

y=xlsread('king1.xlsx', 'B:B');

z=xlsread('king1.xlsx', 'C:C');

a=xlsread('king2.xlsx', 'A:A');

b=xlsread('king2.xlsx', 'B:B');

c=xlsread('king2.xlsx', 'C:C');

xyz=[x y z];

abc=[a b c];

rng(1);

[idx1,C1] = kmeans(xyz,100,'distance','sqEuclidean','MaxIter',500, 'Replicates', 10);

[idx2,C2] = kmeans(abc,100,'distance','sqEuclidean','MaxIter',500, 'Replicates', 10);

[dist,idx3] = pdist2(xyz, C1, 'euclidean', 'Smallest',1);

newVar = xyz(idx3 ,:);

plot3(newVar(:,1), newVar(:,2), newVar(:,3), 'bx');

hold on;

xlabel ('x - axis', 'fontsize', 12);

ylabel ('y - axis', 'fontsize', 12);

zlabel ('z - axis', 'fontsize', 12);

grid

[dist2,idx4] = pdist2(abc, C2, 'euclidean', 'Smallest',1);

newVar2 = abc(idx4 ,:);

plot3(newVar2(:,1), newVar2(:,2), newVar2(:,3), 'r*')

newVar3 = mean (newVar)

newVar4 = mean (newVar2)

newVar5 = (newVar3 + newVar4)/ 2

plot3(newVar5(:,1), newVar5(:,2), newVar5(:,3), 'go');

m=[newVar(:,1) newVar(:,2) newVar(:,3)];

n=[newVar2(:,1) newVar2(:,2) newVar2(:,3)];

o=[newVar5(:,1) newVar5(:,2) newVar5(:,3)];

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darova 2019-5-28

Do you have a question?

Mehmet Volkan Ozdogan 2019-5-28

I could not make the calculation..

I need to find the distance between d2-d1

X in figure are represented by variable m in code,

* in figure are represented by variable n in code,

and the center of cross section is represented by variable o in code

thank you

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Answer 1

darova 2019-5-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/464446-distance-difference-from-center#answer_376970

在 MATLAB Online 中打开

short_example.m

I did this

xyz0 = (mean(xyz)+mean(abc))/2;                % O point
XYZ0 = repmat(xyz0,size(xyz,1),1);             % duplicate rows
d1 = XYZ0 - xyz;                               % Distance(s) between O and X   (d1)
    % find the nearest * to X
D = pdist2(xyz,abc);                           % every possible combinations
D(D==0) = max(D(:));                           % fill zeros with max    ( (:) - convert matrix to column vector )
[~,ind] = min(D(:));                           % find index of min element
    % Found index of min element in vector. Find correspoding indices of points
[i,j] = ind2sub(size(D),ind);                  % extract row and column (i - index of xyz, j - index of abc)
    % calculate the distance between O and * (which is nearest X)  (d2)
d2 = xyz0 - abc(j,:);                          % difference between O point and * (nearest X)
D2 = repmat(d2,size(d2,1),1);                  % duplicate rows
d = D2 - d1;                                   % distance(s) between d2 and d1

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Mehmet Volkan Ozdogan 2019-5-28

编辑：Mehmet Volkan Ozdogan 2019-5-28

在 MATLAB Online 中打开

Thank you for your answer and clear explanation

But I think i could not tell my self clearly,sorry about that,

In my current code i did not use xyz and abc, i used them to find the "newVar" and "newVar2"

"newVar" = X and "newVar2" = *, and also "newVar5"= o

Also i need the distance but "d1 = XYZ0 - xyz" gives coordinate.

I changed the variables and also changed the distance calculation but i have still a problem with the code . Because results are not sensible.

On the other hand i do not understand why you duplicated the rows

Do you have any other suggestion, thank you...

clc;clear;
x=xlsread('king1.xlsx', 'A:A');
y=xlsread('king1.xlsx', 'B:B');
z=xlsread('king1.xlsx', 'C:C');
a=xlsread('king2.xlsx', 'A:A');
b=xlsread('king2.xlsx', 'B:B');
c=xlsread('king2.xlsx', 'C:C');
xyz=[x y z];
abc=[a b c];
rng(1);
[idx1,C1] = kmeans(xyz,100,'distance','sqEuclidean','MaxIter',500, 'Replicates', 10);
[idx2,C2] = kmeans(abc,100,'distance','sqEuclidean','MaxIter',500, 'Replicates', 10);
[dist,idx3] = pdist2(xyz, C1, 'euclidean', 'Smallest',1);
newVar = xyz(idx3 ,:);
plot3(newVar(:,1), newVar(:,2), newVar(:,3), 'bx');
hold on;
xlabel ('x - axis', 'fontsize', 12);
ylabel ('y - axis', 'fontsize', 12);
zlabel ('z - axis', 'fontsize', 12);
grid
[dist2,idx4] = pdist2(abc, C2, 'euclidean', 'Smallest',1);
newVar2 = abc(idx4 ,:);
plot3(newVar2(:,1), newVar2(:,2), newVar2(:,3), 'r*')
newVar3 = mean (newVar)
newVar4 = mean (newVar2)
newVar5 = (newVar3 + newVar4)/ 2
plot3(newVar5(:,1), newVar5(:,2), newVar5(:,3), 'go');
%m=[newVar(:,1) newVar(:,2) newVar(:,3)];
%n=[newVar2(:,1) newVar2(:,2) newVar2(:,3)];
%o=[newVar5(:,1) newVar5(:,2) newVar5(:,3)];
newVar52 = repmat(newVar5,size(newVar,1),1);                         % duplicate rows
[d1,idx5] = pdist2(newVar52, newVar, 'euclidean', 'Smallest',1);     % Distance(s) between O and X   (d1)
             % find the nearest * to X
D = pdist2(newVar,newVar2);                                       % every possible combinations
D(D==0) = max(D(:));                                              % fill zeros with max    ( (:) - convert matrix to column vector )
[~,ind] = min(D(:));                                              % find index of min element
    % Found index of min element in vector. Find correspoding indices of points
[i,j] = ind2sub(size(D),ind);                                    % extract row and column (i - index of xyz, j - index of abc)
    % calculate the distance between O and * (which is nearest X)  (d2)
[d2,idx6] = pdist2(newVar5, newVar2(j,:), 'euclidean', 'Smallest',1);       % difference between O point and * (nearest X)
D2 = repmat(d2,size(d2,1),1);                                                % duplicate rows
d = D2 - d1;   

darova 2019-5-29

在 MATLAB Online 中打开

Sorry. forgot about that. Those are not coordinates, when you subract coordinates you get coordinates difference

p1(x1,y1) - p2(x2,y2) = v(dx,dy)

xyz0 = (mean(xyz)+mean(abc))/2;                % O point (ONE point)
XYZ0 = repmat(xyz0,size(xyz,1),1);             % duplicate rows
d1 = XYZ0 - xyz;                               % difference(s) between O and X (dy,dy,dz)
d1 = sqrt(sum(d1.^2,2));                       % absolute distance(s) (euclidean)
    % the same because xyz0 - one point
d1 = pdist(xyz0,xyz);
    % or
d1 = pdist2(xyz0,xyz,'euclidean','smallest',1)

I duplicated rows, because forgot how pdist2() works

Distance between O and X (d1)
Than i need to find the nearest * to X, - i misunderstood you here
Than calculate the distance between O and * (which is nearest X) (d2)
And lastly i need to calculate the difference between (d1) and (d2)

Try this:

d1 = pdist2(varO,varX);                            % distance(s) (many) between O and X
% varS == var*
[~,idx] = pdist2(varS,varX,'euclidean','smallest',1);    % indices of nearest * for EACH X
d2 = pdist2(varO,varS(idx));                       % distance(s) between O and * (nearest to X)
d2 - d1

Mehmet Volkan Ozdogan 2019-5-29

Thank you for your helps,

I made a little uptade on your code

d2 = pdist2(varO,varS(idx)); have to be ;

d2 = pdist2(varO,varS(idx, :))

thank you again

Mehmet Volkan Ozdogan 2019-5-29

编辑：Mehmet Volkan Ozdogan 2019-5-29

works great thank you again...

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Answer 2

e_oksum 2019-5-29

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/464446-distance-difference-from-center#answer_377022

在 MATLAB Online 中打开

hi mehmet, here is an example code performing what you explained,

example uses random positions, you can adopt by yours..and also simplify it for more compact without plotting etc..

X=rand(1,10)*10       ;% your x position of X
Y=rand(1,10)*10      ;% your y position of X
xs=rand(1,10)*10      ;% your x position of *
ys=rand(1,10)*10      ;% your y position of *
xo=5      ;% center x
yo=5      ;% center y
plot(X,Y,'ro','markerfacecolor','r');
hold on
plot(xs,ys,'k+');
plot(xo,yo,'go','markerfacecolor','g');
for i=1:numel(X)
d1(i)=sqrt((X(i)-xo).^2+(Y(i)-yo).^2);% distance d1 of X(i) Y(i) to center
%find position of nearest xs,ys to X,Y
L=sqrt((xs-X(i)).^2 + (ys-Y(i)).^2);
idx=find(L==min(L));
xp(i)=xs(idx); %(xp yp are the nearest nearest X)
yp(i)=ys(idx);
d2(i)=sqrt((xp(i)-xo).^2 + (yp(i)-yo).^2); % distance d2 of nearest xp yp to X(i),Y(i)
diffd1d2(i)=(d1(i)-d2(i)); % diffrence between d1 d2
% check by plot
l1=plot([X(i) xo],[Y(i) yo],'-r'); % line d1
l2=plot([xp(i) xo],[yp(i) yo],'-k'); % line d2
pause(1)
delete(l1)
delete(l2)
end
list=[X' Y' xp' yp' d1' d2' diffd1d2']

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Mehmet Volkan Ozdogan 2019-5-29

Thank you for your helps and advice, i solve my problem with previous answer.

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Distance difference from center

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