Interpolating data from a look up table

Question

read the look up table

LUT = np.genfromtxt(\'test.out\', delimiter=\',\', dtype=float)
LUT:
    12, 25, 136, 6743
    13, 26, 139, 6786
    14, 27, 142, 67         


        

Answer 1

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]