scipy-interp-bug.py

#!/usr/bin/env python3
import sys
import numpy as np
from scipy.interpolate import interp1d, interp2d

np.set_printoptions(suppress=True, linewidth=120)

k = 10

source1d = np.float64([0]*(2*k-1) + [1]*(2*k-1))
source2d = np.float64([source1d] * (2*k-1))

edge = 2*k-1 - 0.5

sampler1d = interp1d(x=np.arange(4*k-2), y=source1d, kind='cubic') # linear, cubic, quintic
sampler2d = interp2d(x=np.arange(4*k-2), y=np.arange(2*k-1), z=source2d, kind='cubic') # linear, cubic, quintic

samplepoints = edge + np.arange(-k, k+0.5, 0.5)
samples1d = sampler1d(samplepoints)
samples2d = sampler2d(samplepoints, k-1)

print(np.vstack([samplepoints - edge, samples1d, samples2d]).T)

# [[-10.           0.00000072   0.00000072]
#  [ -9.5         -0.           0.        ]
#  [ -9.          -0.00000267  -0.00000267]
#  [ -8.5         -0.          -0.        ]
#  [ -8.           0.00000996   0.00000996]
#  [ -7.5          0.           0.        ]
#  [ -7.          -0.00003719  -0.00003719]
#  [ -6.5         -0.          -0.        ]
#  [ -6.           0.00013879   0.00013879]
#  [ -5.5          0.           0.        ]
#  [ -5.          -0.00051796  -0.00051796]
#  [ -4.5          0.          -0.        ]
#  [ -4.           0.00193304   0.00193304]
#  [ -3.5          0.           0.        ]
#  [ -3.          -0.00721421  -0.00721421]
#  [ -2.5          0.          -0.        ]
#  [ -2.           0.02692379   0.02692379]
#  [ -1.5          0.           0.        ]
#  [ -1.          -0.10048095  -0.10048095]
#  [ -0.5         -0.          -0.        ]
#  [  0.           0.5          0.5       ]
#  [  0.5          1.           1.        ]
#  [  1.           1.10048095   1.10048095]
#  [  1.5          1.           1.        ]
#  [  2.           0.97307621   0.97307621]
#  [  2.5          1.           1.        ]
#  [  3.           1.00721421   1.00721421]
#  [  3.5          1.           1.        ]
#  [  4.           0.99806696   0.99806696]
#  [  4.5          1.           1.        ]
#  [  5.           1.00051796   1.00051796]
#  [  5.5          1.           1.        ]
#  [  6.           0.99986121   0.99986121]
#  [  6.5          1.           1.        ]
#  [  7.           1.00003719   1.00003719]
#  [  7.5          1.           1.        ]
#  [  8.           0.99999004   0.99999004]
#  [  8.5          1.           1.        ]
#  [  9.           1.00000267   1.00000267]
#  [  9.5          1.           1.        ]
#  [ 10.           0.99999928   0.99999928]]