what is the best method to generate random points

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?

[hmi amid]

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.

Answer 1

[Image Analyst]

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