从查找表插入数据 [英] Interpolating data from a look up table

问题描述

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:

Values to be read from the LUT are as follows:

x1, x2, x3 = 12.5, 25.5, 137

为每个给定值(3 列)读取 LUT 中相邻的两个值，我必须对结果进行线性插值(LUT 中的第 4 列).

Reading the neighboring two values in the LUT for each of the given values (3 columns), I have to linearly interpolate the results (4th column in LUT).

给定的值 (x1, x2, x3) 属于 LUT 的第 1 行和第 2 行之间.基于此如何读取第一行和第二行之间的结果?

The given values (x1, x2, x3) belongs to between 1st and 2nd row of the LUT. Based on this how to read the results between 1st and 2nd row?

推荐答案

给定要插入的坐标列表 coords，可以使用 scipy.spatial.cKDTree 获取表格中线性插值所需的 2 个最接近的条目.下面的代码显示了一个使用示例，已经矢量化.

Given a list of coordinates coords where you want to interpolate, you can use scipy.spatial.cKDTree to obtain the 2 closest entries of your table that are necessary for the linear interpolation. The code below shows an usage example, already vectorized.

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]

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