Interpolation 1D

interp1d interpolates 1D scattered data using linear or cubic spline methods. It is backed by Cython for speed and handles duplicate x-coordinates gracefully (first occurrence is used).

Linear interpolation

import numpy as np
from pflm.interp import interp1d

x = np.linspace(0, 1, 11)
y = np.sin(2 * np.pi * x)

xq = np.linspace(0, 1, 51)
yq = interp1d(x, y, xq, method="linear")
print("Query shape:", yq.shape)  # (51,)

Spline interpolation

Use method="spline" for smoother results when the underlying function is expected to be smooth.

yq_spline = interp1d(x, y, xq, method="spline")

# Compare max absolute error
y_true = np.sin(2 * np.pi * xq)
print("Linear  max-err:", np.max(np.abs(interp1d(x, y, xq, method='linear') - y_true)))
print("Spline  max-err:", np.max(np.abs(yq_spline - y_true)))