如何绘制一个圆圈？

Question

下面的代码在Matlab中绘制圆圈.如何指定MarkerEdgeColor和MarkerFaceColor中.

function plot_model
exit_agents=csvread('C:\Users\sony\Desktop\latest_mixed_crowds\December\exit_agents.csv');
%scatter(exit_agents(:,2),exit_agents(:,3),pi*.25^2,'filled');
for ii =1:size(exit_agents,1),
    circle(exit_agents(ii,2),exit_agents(ii,3),0.25);
end
end
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

使用绘图和散射在缩放时奇怪地缩放它们.这不是我想要的.

Answer 1

绘制圆圈有多种选择.最简单的是,实际绘制一个充满rectangle曲率的曲线:

%// radius
r = 2;

%// center
c = [3 3];

pos = [c-r 2*r 2*r];
r = rectangle('Position',pos,'Curvature',[1 1], 'FaceColor', 'red', 'Edgecolor','none')
axis equal

通过使用R2014b更新图形引擎,这非常顺利:

如果你有一个比R2014b更旧的Matlab版本,你需要坚持使用三角学方法,但是用fill它来填充它:

%// radius
r = 2;
%// center
c = [3 3];
%// number of points
n = 1000;
%// running variable
t = linspace(0,2*pi,n);

x = c(1) + r*sin(t);
y = c(2) + r*cos(t);

%// draw filled polygon
fill(x,y,[1,1,1],'FaceColor','red','EdgeColor','none')
axis equal

该"决议"通过点数可以自由缩放n.

那么你的功能可能就像

function h = circle(x,y,r,MarkerFaceColor,MarkerEdgeColor)
hold on
c = [x y];
pos = [c-r 2*r 2*r];
r = rectangle('Position',pos,'Curvature',[1 1], ...
    'FaceColor', MarkerFaceColor, 'Edgecolor',MarkerEdgeColor)
hold off
end