f I have a circle and i generated 50 random points inside , how can i assign unique id to every random point inside it , i want to have like user(1),us​er(2),....​.,user(50) ? so i can call any point inside the circle with this id

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Meme
Meme 2014-4-2
评论： Meme 2014-4-3
f I have a circle in matlab and i generated 50 random points inside , how can i assign unique id to every random point inside it , i want to have like user(1),user(2),.....,user(50) ? so i can call any point inside the circle with this id i have these two codes to make a circle and generate the random points inside it if I have a circle and i generated 50 random points inside , how can i assign unique id to every random point inside it , i want to have like user(1),user(2),.....,user(50) ? so i can call any point inside the circle with this id i have these two codes to make a circle and generate the random points iside it
%%// Plot the circle
x = linspace(-sqrt(10),sqrt(10));
y1 = sqrt(10-x.^2);
y2 = -sqrt(10-x.^2);
plot(x,y1,x,y2)
axis equal
%%// Choose from 1000 random point pairs
c=[0 0];
N = 1000;
%%// Radius of circle
radius = sqrt(10);
%%// Create a random point matrix Nx2
points_mat = [ radius*2*(rand(N,1)-0.5) radius*2*(rand(N,1)-0.5)];
%%// Select the first 50 pairs that lies inside circle
ind1 = find(sqrt( points_mat(:,1).^2 + points_mat(:,2).^2 )<radius); points_mat=points_mat(ind1(1:50),:);
%%// Plot the 50 points on the circle
hold on
text(0,0,' Center') %%// Center
text(points_mat(:,1),points_mat(:,2),'n') %%// 50 points
%// Set parameters
R = 15; %// radius
C = [0 0]; %// center [x y]
N = 50; %// number of points inside circle
%// generate circle boundary
t = linspace(0, 2*pi, 100);
x = R*cos(t) + C(1);
y = R*sin(t) + C(2);
%// generate random points inside it
th = 2*pi*rand(N,1);
r = R*rand(N,1);
xR = r.*cos(th) + C(1);
yR = r.*sin(th) + C(2); zR=[xR yR];
%// Plot everything
figure(1), clf, hold on
plot(x,y,'b') plot(C(1),C(2),'r.', 'MarkerSize', 60)
plot(xR,yR,'p')
axis equal

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回答（2 个）

Image Analyst
Image Analyst 2014-4-2
I don't understand. xR HAS a unique label for every point - it's the index! You don't need anything more. However if you want it as a separate row, then do
newX = [1:length(xR); xR];
Walter Roberson
Walter Roberson 2014-4-2
Store the coordinates in a 2D matrix and use the row number, so user(5,:) for example.
Or use a cell array and use {} instead of (), so user{5} for example.

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