How do I plot a circle with a given radius and center?

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MathWorks Support Team 2010-7-26

7
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https://ww2.mathworks.cn/matlabcentral/answers/98665-how-do-i-plot-a-circle-with-a-given-radius-and-center

回答： Shengchao Lin 2023-8-11

采纳的回答： MathWorks Support Team

I would like to plot a circle with a given radius and center.

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Answer 1

MathWorks Support Team 2024-9-4

28
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https://ww2.mathworks.cn/matlabcentral/answers/98665-how-do-i-plot-a-circle-with-a-given-radius-and-center#answer_108013

编辑：MathWorks Support Team 2022-3-23

在 MATLAB Online 中打开

Here is a MATLAB function that plots a circle with radius 'r' and locates the center at the coordinates 'x' and 'y':

function h = circle(x,y,r)
hold on
th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y;
h = plot(xunit, yunit);
hold off

An alternative method is to use the 'rectangle' function:

function h = circle2(x,y,r)
d = r*2;
px = x-r;
py = y-r;
h = rectangle('Position',[px py d d],'Curvature',[1,1]);
daspect([1,1,1])

If you are using version R2012a or later and have Image Processing Toolbox, then you can use the 'viscircles' function to draw circles:

viscircles(centers,radii)

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Image Analyst 2022-9-9

在 MATLAB Online 中打开

@Yuvin Wickramanayake no. It means that you put that code into a script, maybe it was called testcircle.m and preceding that code you had code to call the function like

h = circle(x, y, r);

At least that's one possibility. If so, you'd need to close your circle() function with the "end" keyword, which will allow a function to be defined and called from within a script.

function h = circle(x,y,r)
hold on
th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y;
h = plot(xunit, yunit);
hold off
end

If you still have trouble, attach your whole m-file in a NEW question (not here).

Walter Roberson 2022-9-9

You would get a different error message if you had a script with a function after and the function did not have a matching end statement.

That error could happen if you try to create a function inside a script in a MATLAB version before R2015b. It might perhaps also happen if you try to define a function at the command line (I seem to remember the wording as being slightly different for that case, but perhaps that is the wording in an older version than I am using.)

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