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87
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1 #!/usr/bin/env python
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2
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3 """
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4 random points in a circle
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5 """
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6 # TODO: a `D`-sphere
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7
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8 import math
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9 import random
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10 import sys
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11 from .cli import DatasetGenerationParser
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12
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13
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14 class CircularRandom(object):
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15
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16 twopi = 2.*math.pi
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17
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18 def __init__(self, center, radius=1.):
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19 """
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20 center -- (x,y) center of circle
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21 """
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22
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23 assert radius > 0
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24 self.center = (x, y) = center
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25 self.radius = radius
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26
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27 def __call__(self, n_points):
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28 """samples `n_points`"""
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29
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30 return [self.point() for _ in xrange(n_points)]
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31
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32 def point(self):
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33 """samples a single point"""
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34 # TODO: because area grows as 1/r, this will bias
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35 # points towards the center. This should be corrected
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36
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37 r = self.radius*random.random()
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38 theta = self.twopi*random.random()
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39 x = math.cos(theta)
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40 y = math.sqrt(1. - x*x)
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41 if theta > math.pi:
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42 y = -y
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43 return (self.center[0] + x*r,
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44 self.center[1] + y*r)
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45
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46
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47 def main(args=sys.argv[1:]):
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48 """CLI"""
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49
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50 # parse command line
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51 parser = DatasetGenerationParser(description=__doc__)
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52 parser.add_argument('--center', dest='center',
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53 nargs=2, metavar=('X', 'Y'),
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54 type=float, default=(0., 0.),
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55 help="center of circle [DEFAULT: %(default)s]")
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56 parser.add_argument('-R', '--radius', dest='radius',
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57 type=float, default=1.,
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58 help="radius of circle [DEFAULT: %(default)s]")
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59 options = parser.parse_args(args)
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60
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61 # instantiate sampler
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62 circle = CircularRandom(options.center, options.radius)
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63
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64 # get writer
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65 writer = parser.writer()
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66
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67 # sample
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68 points = circle(options.number)
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69
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70 # output
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71 writer.writerows(points)
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72
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73 if __name__ == '__main__':
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74 main()
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