# udacity373_code / unit3 / u3-12_creating_particles.py

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129``` ``` # Now we want to create particles, # p[i] = robot(). In this assignment, write # code that will assign 1000 such particles # to a list. # # Your program should print out the length # of your list (don't cheat by making an # arbitrary list of 1000 elements!) # # Don't modify the code below. Please enter # your code at the bottom. from math import * import random landmarks = [[20.0, 20.0], [80.0, 80.0], [20.0, 80.0], [80.0, 20.0]] world_size = 100.0 class robot: def __init__(self): self.x = random.random() * world_size self.y = random.random() * world_size self.orientation = random.random() * 2.0 * pi self.forward_noise = 0.0; self.turn_noise = 0.0; self.sense_noise = 0.0; def set(self, new_x, new_y, new_orientation): if new_x < 0 or new_x >= world_size: raise ValueError, 'X coordinate out of bound' if new_y < 0 or new_y >= world_size: raise ValueError, 'Y coordinate out of bound' if new_orientation < 0 or new_orientation >= 2 * pi: raise ValueError, 'Orientation must be in [0..2pi]' self.x = float(new_x) self.y = float(new_y) self.orientation = float(new_orientation) def set_noise(self, new_f_noise, new_t_noise, new_s_noise): # makes it possible to change the noise parameters # this is often useful in particle filters self.forward_noise = float(new_f_noise); self.turn_noise = float(new_t_noise); self.sense_noise = float(new_s_noise); def sense(self): Z = [] for i in range(len(landmarks)): dist = sqrt((self.x - landmarks[i][0]) ** 2 + (self.y - landmarks[i][1]) ** 2) dist += random.gauss(0.0, self.sense_noise) Z.append(dist) return Z def move(self, turn, forward): if forward < 0: raise ValueError, 'Robot cant move backwards' # turn, and add randomness to the turning command orientation = self.orientation + float(turn) + random.gauss(0.0, self.turn_noise) orientation %= 2 * pi # move, and add randomness to the motion command dist = float(forward) + random.gauss(0.0, self.forward_noise) x = self.x + (cos(orientation) * dist) y = self.y + (sin(orientation) * dist) x %= world_size # cyclic truncate y %= world_size # set particle res = robot() res.set(x, y, orientation) res.set_noise(self.forward_noise, self.turn_noise, self.sense_noise) return res def Gaussian(self, mu, sigma, x): # calculates the probability of x for 1-dim Gaussian with mean mu and var. sigma return exp(- ((mu - x) ** 2) / (sigma ** 2) / 2.0) / sqrt(2.0 * pi * (sigma ** 2)) def measurement_prob(self, measurement): # calculates how likely a measurement should be prob = 1.0; for i in range(len(landmarks)): dist = sqrt((self.x - landmarks[i][0]) ** 2 + (self.y - landmarks[i][1]) ** 2) prob *= self.Gaussian(dist, self.sense_noise, measurement[i]) return prob def __repr__(self): return '[x=%.6s y=%.6s orient=%.6s]' % (str(self.x), str(self.y), str(self.orientation)) def eval(r, p): sum = 0.0; for i in range(len(p)): # calculate mean error dx = (p[i].x - r.x + (world_size/2.0)) % world_size - (world_size/2.0) dy = (p[i].y - r.y + (world_size/2.0)) % world_size - (world_size/2.0) err = sqrt(dx * dx + dy * dy) sum += err return sum / float(len(p)) #myrobot = robot() #myrobot.set_noise(5.0, 0.1, 5.0) #myrobot.set(30.0, 50.0, pi/2) #myrobot = myrobot.move(-pi/2, 15.0) #print myrobot.sense() #myrobot = myrobot.move(-pi/2, 10.0) #print myrobot.sense() #### DON'T MODIFY ANYTHING ABOVE HERE! ENTER CODE BELOW #### N = 1000 p = [] #enter code here p = [robot() for i in range(0, N)] print len(p) ```