Points Elimination

Jijo Ninan

2011 3 15

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i have a set of 10 point of circle

1.For each three successive points , calculate the radius of the circle passing through these points

2. using this points i have to find three points having the maximum radius, then remove the middle point from set

3.for all points repeat steps 1 and 2 until only three points remain

i have the formula for finding radius but i cannot solve the 2 & 3 step.

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Jijo Ninan 2011-3-15

This is what i have done but next three steps i am stuck up

function[Oxi,Oyi,Ri,PCx,PCy]= Rough(a,b,c,d,e,a1,b1,c1,d1,e1,x1,y1,x2,y2,x3,y3,x4,y4,x5,y5)

% calculate the center of the circle

%circle coordiantes three points (x1,y1)(x2,y2)(x3,y3)

%coordinates of center of circle

a=y3-y1;

b=y2-y1;

c=x2-x1;

d=x3-x1;

e=y3-y1;

a1=y3+y1;

b1=y2+y1;

c1=x2+x1;

d1=x3+x1;

e1=x3-x2;

fprintf('co-ordinates of center of the circle are ')

Oxi=(a*(c*c1+b*b1)-b*(d*d1+a*a1)/(2*(c*e-b*e1)));

Oyi=(c*(d*d1+a*a1)-d*(c*c1+b*b1)/(2*(c*e-b*e1)));

%Radius of circle;

Ri=sqrt((x1-Oxi)^2)+((y1-Oyi)^2);

disp('radius of a circle');

disp(Ri);

arra=[x1,x2,x3,x4,x5];

arra2=[y1,y2,y3,y4,y5];

meanx=mean(arra);

meany=mean(arra2);

disp('mean of x values');

disp(meanx);

disp('mean of y values');

disp(meany);

PCx=meanx;

PCy=meany;

plot(x1,y1,x2,y2,x3,y3,x4,y4,x5,y5);

for calling the function

fileName='C:\Users\Jijo\Desktop\MATLAB1\import.xls'

a=xlsread(fileName);

x1=a(1,1)

x2=a(2,1)

x3=a(3,1)

y1=a(1,2)

y2=a(2,2)

y3=a(3,2)

x4=a(4,1)

y4=a(4,2)

x5=a(5,1)

y5=a(5,2)

a=y3-y1;

b=y2-y1;

c=x2-x1;

d=x3-x1;

e=y3-y1;

a1=y3+y1;

b1=y2+y1;

c1=x2+x1;

d1=x3+x1;

e1=x3-x2;

[Oxi,Oyi,Ri,PCx,PCy]= Rough(a,b,c,d,e,a1,b1,c1,d1,e1,x1,y1,x2,y2,x3,y3,x4,y4,x5,y5)

Jan 2011-3-15

Please insert the code by editing your original messge.

Walter Roberson 2011-3-18

I can't tell if step #1 is to be applied over the entire list first, and then step #2 is to eliminate one of the points, then apply step #1 to all of the reduced list, and so on?

Or is step #1 to be applied to the first 3 points, then one of those removed by step #2, then one more point added from the original 10, then remove 1, and so on?

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