Does anyone know how to use the matlab to calculate the minimu distance between a point outside oval and the oval surface?
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huazai2020
am 28 Jun. 2020
Bearbeitet: huazai2020
am 18 Jul. 2020
Does anyone know how to use the matlab to calculate the minimu distance between a point outside oval and the oval surface?
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Matt J
am 30 Jun. 2020
Bearbeitet: Matt J
am 30 Jun. 2020
You can use trustregprob from the File Exchange
For example, consider the following ellipse and external point y,
A=[2 1;1,2]; %Ellipse equation matrix
y=[1;0.5]; %External point
z=[0.584808315593597 ; 0.201052451754066]; %Closest point
ellipsefun=@(p,q) sum([p;q].*(A*[p;q]))-1 ;
hold on
fimplicit(ellipsefun, [-1 1.3 -1 1.3])
plot(y(1),y(2),'rx',z(1),z(2),'bo');
axis equal
hold off
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/324112/image.png)
I found the closest point z using the code below,
Aroot=chol(A);
L=Aroot\eye(2);
z=Aroot\trustregprob(L.'*L, L.'*y,1);
and the minimum distance is just,
>> distance=norm(z-y)
distance =
0.5116
20 Kommentare
Bruno Luong
am 8 Jul. 2020
FEX short word for File Exchange. Click on it I put the link on my message.
H1: https://www.mathworks.com/help/matlab/matlab_prog/add-help-for-your-program.html
Weitere Antworten (2)
Image Analyst
am 4 Jul. 2020
"The oual can be both given in the form of an equation or data points." <== if you have data points (xb, yb) on the boundary of an ellipse/oval, you can use sqrt() to find the distances to some other point (xp, yp). Then use in() to find the minimum distance.
distances = sqrt(xb-xp).^2 + (yb-yp).^2);
minDistance = min(distances)
If you have an image then you need to get the boundary points first:
boundaries = bwboundaries(binaryImageOfEllipse);
boundaries = boundaries{1}; % Extract double array from cell array.
xb = boundaries(:, 2);
yb = boundaries(:, 1);
10 Kommentare
Image Analyst
am 18 Jul. 2020
No, you shouldn't use an inner loop because your minDistance will just be the distance between (x1,y1) and xwoint(Num2) and ywoint(Num2) instead of the whole array. Do it like this:
clc;
clear all;
A = xlsread('data1.xlsx');
xpoint=A(:,1);
ypoint=A(:,2);
Num1=length(xpoint);
xwoint=A(:,3);
ywoint=A(:,4);
Num2=length(xwoint);
for k=1:1:Num1
x1 = xpoint(k);
y1 = ypoint(k);
distances = sqrt((xwoint-x1).^2 + (ywoint-y1).^2);
minDistance(k) = min(distances)*1000;
end
plot(minDistance, 'b-');
% xlswrite('thick.xlsx',minDistance,'sheet1');
Not sure why you wanted to multiply by 1000 though.
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