how do I reference the distance of any points from the center of a uniform distribution in a circle

Question

zaxtronix 2016-5-13

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/284020-how-do-i-reference-the-distance-of-any-points-from-the-center-of-a-uniform-distribution-in-a-circle

评论： Walter Roberson 2016-5-13

I have done a uniform distribution of n number of points in a circle, I am stuck in trying to reference the distance of any of those points from the center of the circle to do a further calculation;

My uniform distribution goes as follows:

% radius of the circle
R = 500;
% number of samples
n = 1000;
% my uniform distribution
angle  = 2 * pi*(rand(1,n));
r = R * sqrt(rand(1,n));
y = r.*sin(angle);
x = r.*cos(angle);
% the plot of the uniform distribution
plot(x,y,'r.');

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2016-5-13

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/284020-how-do-i-reference-the-distance-of-any-points-from-the-center-of-a-uniform-distribution-in-a-circle#answer_221972

在 MATLAB Online 中打开

distances = sqrt(x.^2 + y.^2);

2 个评论
显示无隐藏无

zaxtronix 2016-5-13

using the Pythagoras formula you gave makes all the distance to be positive, and the coordinates at the negative sections of the plot will not be seen, i.e (at x = -20, y = -30). Is this the only way ?

Walter Roberson 2016-5-13

在 MATLAB Online 中打开

By definition, the distance of an object to itself is 0: that is true for all distance metrics, part of the definition of a metric space. In order for a distance function to return a negative value, you would need it to be the case that some point B is even closer to point A then A is to itself. That makes no sense. Distances are never negative.

The way you construct your data, all of the distances will be r

Possibly what you are looking for is direction information. For that, use

atan2(y, x)

请先登录，再进行评论。