在python中计算boid的邻域

Question

我正在编写一个程序，通过boids来模拟蟒蛇中的一群鸟。其中一项任务是计算邻接体的数量(distance <= 50)。我试着这样做(见代码)，但我没有得到好的结果。“打印距离”给出了20倍的相同距离，所以我假设我计算的是相同的几个体块20倍。我需要所有的组合。我是编程新手，所以欢迎任何帮助！

WIDTH = 1000            # WIDTH OF SCREEN IN PIXELS
HEIGHT = 500            # HEIGHT OF SCREEN IN PIXELS
BOIDS = 20              # NUMBER OF BOIDS IN SIMULATION
SPEED_LIMIT = 500       # FOR BOID VELOCITY
BOID_EYESIGHT = 50      # HOW FAR A BOID CAN LOOK
WALL = 50               # FROM SIDE IN PIXELS
WALL_FORCE = 100        # ACCELERATION PER MOVE


################################################################################

import random
from math import sqrt

X = 0
Y = 1
VX = 2
VY = 3

boids = []

for i in range(BOIDS):
    b_pos_x = random.uniform(0,WIDTH)
    b_pos_y = random.uniform(0,HEIGHT)
    b_vel_x = random.uniform(-100,100)
    b_vel_y = random.uniform(-100,100)
    b = [b_pos_x, b_pos_y, b_vel_x, b_vel_y]

    boids.append(b)

# definition of functions:

def calculate_distance(a,b):                       # calculates distance between two boids
    distance = sqrt((a[X] - b[X])**2 + (a[Y] - b[Y])**2)
    return distance

def value_velocity(v):                             # calculates velocity of boids
    velocity = sqrt(v[VX]**2+v[VY]**2)
    return velocity

##############

for element_1 in range(len(boids)):             
    for element_2 in range(len(boids)):
        if element_1 != element_2:                    # for two different boids:
            distance = calculate_distance(boids[element_1],boids[element_2]) 
                 # calculate distance between boids

    velocity = value_velocity(boids[element_1])             # calculate velocity of boids

neighbors = 0                      # start neighbor counter

for element_1 in range(len(boids)):
    for element_2 in range(len(boids)):
        if element_1 != element_2:          # for diferent boids
            if distance <= 50:              # with a distance of <=50
                neighbors += 1              # add +1 to neighbor counter
    print distance

Answer 1

您应该将距离设置为数组或合并两个循环。因为目前您总是使用在第一对for循环中计算的最后一个distance值。

例如，您可以通过以下方式修改您的代码：

distance=[[calculate_distance(boids[i],boids[j]) for j in range(len(boids))] for i in range(len(boids))]

for element_1 in range(len(boids)):
    for element_2 in range(len(boids)):
        if element_1 != element_2:          # for diferent boids
            if distance[element_1][element_2] <= 50:              # with a distance of <=50
                neighbors += 1
                print distance[element_1][element_2]

你也可以只做第一个循环中的所有邻居计算：

neighbors =0
for element_1 in range(len(boids)):             
    for element_2 in range(len(boids)):
        if element_1 != element_2:                    # for two different boids:
            distance = calculate_distance(boids[element_1],boids[element_2]) 
            if distance <=50:
               neighbors += 1