what is the best method to generate random points

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Hassan
Hassan 2017-5-1
回答： Image Analyst 2017-5-1
Hi,
Suppose i have a set of points such as (x,y) vector:
1.3300 8.8900
0.8800 7.0200
0.7500 4.9800
2.2200 4.3500
3.1300 1.9200
1.7400 1.3700
1.8900 0.7700
4.0100 0.3100
6.0800 1.3400
7.3400 1.3800
8.4500 0.6900
8.6000 0.5300
9.2700 1.4900
8.9900 2.4500
7.6700 4.1700
7.5500 5.7900
9.3900 6.4400
8.9300 7.0000
9.2000 8.6900
9.4600 9.3600
8.8600 8.7400
7.2300 7.0500
5.8900 8.0600
5.0000 9.0000
2.8300 9.8800
what is the best method/function to generate random points within?
  1 个评论
hmi amid
hmi amid 2017-5-1
Do you mean random points that are already in this matrix (x,y)? Or new random points in the range of this matrix? For the first meaning you can use :
Suppose your set of points is in V
i=ceil(rand(1)*length(V));
x_random=V(i,1);y_random=V(i,2);
For the second case:
x_random=min(V(:,1))+rand(1)*(max(V(:,1))-min(V(:,1)));
y_random=min(V(:,2))+rand(1)*(max(V(:,2))-min(V(:,2)));
Best, Amid.

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Image Analyst
Image Analyst 2017-5-1
Try this:
xy = [...
1.3300 8.8900
0.8800 7.0200
0.7500 4.9800
2.2200 4.3500
3.1300 1.9200
1.7400 1.3700
1.8900 0.7700
4.0100 0.3100
6.0800 1.3400
7.3400 1.3800
8.4500 0.6900
8.6000 0.5300
9.2700 1.4900
8.9900 2.4500
7.6700 4.1700
7.5500 5.7900
9.3900 6.4400
8.9300 7.0000
9.2000 8.6900
9.4600 9.3600
8.8600 8.7400
7.2300 7.0500
5.8900 8.0600
5.0000 9.0000
2.8300 9.8800];
x = xy(:, 1);
y = xy(:, 2);
% Show the points
% subplot(2, 2, 1);
plot(x, y, 'b-', 'LineWidth', 2);
grid on;
hold on;
% Find ranges
minX = min(x)
maxX = max(x)
minY = min(y)
maxY = max(y)
% Decide on number of points
numRandomPoints = 1000;
pointCount = 0;
while pointCount < numRandomPoints
thisPointX = (maxX - minX) * rand() + minX;
thisPointY = (maxY - minY) * rand() + minY;
if inpolygon(thisPointX, thisPointY, x, y)
plot(thisPointX, thisPointY, 'r.', 'MarkerSize', 14);
pointCount = pointCount + 1;
end
end

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