How to plot a circle?

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Ara 2013-1-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/58242-how-to-plot-a-circle

Hi Everybody,

I am trying to plot a circle with radius= 190 km, and the centre of circle is (2.55, 101.46)both are in degree. If I have to change in km also are become like this (283.87, 11295.0345)km. The question is how can I determine the centre of circle by symbol? and the sketch has been attached here would be useful because I do not know how to plot like this? Could you please help me?

http://www.sendspace.com/file/9w4sx8

radius = 190;
centerX = 2.55;
centerY = 101.46;
rectangle('Position',[centerX, centerY, radius, radius],...
    'Curvature',[1,1],...
    'FaceColor','w');
axis square;

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Image Analyst 2013-1-8

I don't know which of the four "download" words to click on on that page. Why don't you try http://snag.gy or tinypic.com?

Ara 2013-1-8

Thank you. I did it. http://snag.gy/N2jVI.jpg

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采纳的回答

Image Analyst 2013-1-8

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https://ww2.mathworks.cn/matlabcentral/answers/58242-how-to-plot-a-circle#answer_70467

I don't know what "determine the centre of circle by symbol" means, but I can tell you from the code that the center of the circle is at (x, y)=(2.55, 101.46) but I don't know what you mean when you say "both are by degree". What does a pair of degrees mean? Aren't x and y in km? How are they in degrees? What does that mean?

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Image Analyst 2013-1-9

在 MATLAB Online 中打开

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
format longg;
format compact;
fontSize = 20;
xy = [...
103.3283737 -1.737315374
105.0218884 1.859952908
103.3256787 -1.731133997
104.614639 -1.186835546
103.7117851 -1.506892036
103.3055487 4.91010298]
x = xy(:, 1);
y = xy(:,2);
  
%CIRCFIT  Fits a circle in x,y plane
%
% [XC, YC, R, A] = CIRCFIT(X,Y)
% Result is center point (yc,xc) and radius R.  A is an optional
% output describing the circle's equation:
%
%   x^2+y^2+a(1)*x+a(2)*y+a(3)=0
n=length(x);  xx=x.*x; yy=y.*y; xy=x.*y;
A=[sum(x) sum(y) n;sum(xy) sum(yy) sum(y);sum(xx) sum(xy) sum(x)];
B=[-sum(xx+yy) ; -sum(xx.*y+yy.*y) ; -sum(xx.*x+xy.*y)];
a=A\B;
xc = -.5*a(1)
yc = -.5*a(2)
R  =  sqrt((a(1)^2+a(2)^2)/4-a(3))

In the command window:

xc =
          101.536580840907
yc =
          1.48302327061266
R =
          3.75388783621146

I just plugged your coordinates into the FAQ. What did you do differently to cause it to throw an error? What is the error?

Ara 2013-1-16

Thank you, Image. Sorry for the late response. Just remain some questions and I am trying to solve it, if I can't fix it I will bother you again.

Image Analyst 2013-1-16

Then perhaps you want this: http://www.mathworks.com/matlabcentral/fileexchange/34767-a-suite-of-minimal-bounding-objects? It will find the smallest circle (or rectangle or triangle, or other redefined shapes) that will contain (fit) all your points inside.

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