scipy 如何在网格内拾取点？

flvlnr44 于 2022-11-10 发布在其他

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我有一个由两个边界数组组成的网格：lon_bnds和lat_bnds。目标是选取网格内的点。
下面是一个例子：

import numpy as np
import matplotlib.pyplot as plt
import pandas as pd

lon_bnds = np.array([[-77.9645  , -77.56074 , -77.162025, -76.76827 , -76.37937 ],
                    [-77.88815 , -77.48613 , -77.08915 , -76.69711 , -76.30993 ],
                    [-77.811676, -77.41139 , -77.01614 , -76.62582 , -76.24034 ],
                    [-77.73638 , -77.337814, -76.944275, -76.55565 , -76.17186 ],
                    [-77.66197 , -77.265114, -76.87326 , -76.48632 , -76.1042  ]])

lat_bnds = np.array([[-77.34674 , -77.35804 , -77.36858 , -77.378395, -77.38752 ],
                    [-77.28847 , -77.299614, -77.31001 , -77.31969 , -77.328674],
                    [-77.23022 , -77.24122 , -77.25147 , -77.26101 , -77.26986 ],
                    [-77.17193 , -77.182785, -77.192894, -77.20229 , -77.211006],
                    [-77.11363 , -77.12434 , -77.13431 , -77.14357 , -77.15215 ]])

plt.scatter(lon_bnds, lat_bnds, label='corner')

d = {'longitude': [-79, -77.2, -77, -75.5], 'latitude': [-77.4, -77.2, -77.3, -77.3]}
df_points = pd.DataFrame(data=d)
plt.scatter(df_points['longitude'], df_points['latitude'], c='r', label='points')

plt.legend()

结果应该是具有两个内部点的DataFrame。
我也发现这个question很有用，但是他们使用kdTree来搜索周围的点，而不是像我的例子那样使用精确的边界数组。

scipy

来源：https://stackoverflow.com/questions/72657458/how-to-pick-points-inside-grids

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按热度按时间

sgtfey8w1#


# !/usr/bin/env python

 """
 Test if query points are inside the convex hull of another set of points.
 """

 import numpy as np
 import pandas as pd

 from scipy.optimize import linprog

 def in_hull(points, x):
     # https://stackoverflow.com/a/43564754/2912349
     n_points = len(points)
     n_dim = len(x)
     c = np.zeros(n_points)
     A = np.r_[points.T,np.ones((1,n_points))]
     b = np.r_[x, np.ones(1)]
     lp = linprog(c, A_eq=A, b_eq=b)
     return lp.success

 if __name__ == '__main__':
     lon_bnds = np.array([[-77.9645  , -77.56074 , -77.162025, -76.76827 , -76.37937 ],
                         [-77.88815 , -77.48613 , -77.08915 , -76.69711 , -76.30993 ],
                         [-77.811676, -77.41139 , -77.01614 , -76.62582 , -76.24034 ],
                         [-77.73638 , -77.337814, -76.944275, -76.55565 , -76.17186 ],
                         [-77.66197 , -77.265114, -76.87326 , -76.48632 , -76.1042  ]])

     lat_bnds = np.array([[-77.34674 , -77.35804 , -77.36858 , -77.378395, -77.38752 ],
                         [-77.28847 , -77.299614, -77.31001 , -77.31969 , -77.328674],
                         [-77.23022 , -77.24122 , -77.25147 , -77.26101 , -77.26986 ],
                         [-77.17193 , -77.182785, -77.192894, -77.20229 , -77.211006],
                         [-77.11363 , -77.12434 , -77.13431 , -77.14357 , -77.15215 ]])

     points = np.c_[lon_bnds.ravel(), lat_bnds.ravel()]

     d = {'longitude': [-79, -77.2, -77, -75.5], 'latitude': [-77.4, -77.2, -77.3, -77.3]}
     df = pd.DataFrame(d)
     df['in hull'] = df[['longitude', 'latitude']].apply(lambda x : in_hull(points, x.values), axis=1)
     print(df)

     #    longitude  latitude  in hull
     # 0      -79.0     -77.4    False
     # 1      -77.2     -77.2     True
     # 2      -77.0     -77.3     True
     # 3      -75.5     -77.3    False

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scipy 如何在网格内拾取点？

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