How to plot a circle?
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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?
radius = 190;
centerX = 2.55;
centerY = 101.46;
rectangle('Position',[centerX, centerY, radius, radius],...
'Curvature',[1,1],...
'FaceColor','w');
axis square;
2 个评论
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
采纳的回答
Image Analyst
2013-1-8
1 个投票
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?
13 个评论
Ara
2013-1-8
Image Analyst
2013-1-8
Are you trying to fit the perimeter of the circle through the centers of those little red ellipses? If so, please refer to the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_fit_a_circle_to_a_set_of_XY_data.3F
Ara
2013-1-9
Image Analyst
2013-1-9
编辑：Image Analyst
2013-1-9
Maybe. But you haven't provided to plot the tiny little red circles. But I don't see where the difficulty lies. You know the centers of the little circles, don't you? And I presume you used the code in your initial question to plot it right? So you just put those centers in to the code in the FAQ, and you get the center and radius of the circle which has its perimeter go through the center of your little red circles. It's trivial. But OK, give me the centers of the little red circles and I'll put it into the FAQ code for you if you're unable to.
Ara
2013-1-9
Image Analyst
2013-1-9
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
2013-1-9
Image Analyst
2013-1-9
You did not share line 34 but I'm sure that's one you can figure out yourself because you already know how to plot circles. Big, small, whatever - it doesn't matter - it's all the same code. It looks like just a simple syntax error anyway.
Image Analyst
2013-1-9
But you already showed how the rectangle function can be used to plot circles. Just change the center and radius.
Ara
2013-1-9
Ara
2013-1-16
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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