从查找表中插入数据

Question

阅读查找表

LUT = np.genfromtxt('test.out', delimiter=',', dtype=float)
LUT:
    12, 25, 136, 6743
    13, 26, 139, 6786
    14, 27, 142, 6791
    15, 28, 145, 6789

要从LUT读取的值如下:

x1, x2, x3 = 12.5, 25.5, 137

对于每个给定值(3列)读取LUT中的相邻两个值,我必须对结果进行线性插值(LUT中的第4列).

给定值(x1,x2,x3)属于LUT的第1行和第2行之间.基于此如何读取第1行和第2行之间的结果？

Answer 1

给定coords要插值的坐标列表,可以使用scipy.spatial.cKDTree获得表格的2个最接近的条目,这些条目是线性插值所必需的.下面的代码显示了一个已经向量化的用法示例.

import numpy as np
from scipy.spatial import cKDTree

# inputs
LTU = np.genfromtxt('test.txt', delimiter=',')

coords = ((12.5, 25.5, 137),
          (13.5, 26.5, 141),
          (14.5, 25.5, 144))

# querying and interpolating
xyz = LTU[:, :3]
val = LTU[:, 3]

del LTU # attempt to clean up memory

tree = cKDTree(xyz)
dist, ind = tree.query(coords, k=2)

d1, d2 = dist.T
v1, v2 = val[ind].T
v = (d1)/(d1 + d2)*(v2 - v1) + v1

print(v)
#[ 6758.73909236  6789.16987298  6790.03575996]