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scipy.signal.

# qspline1d_eval

scipy.signal.qspline1d_eval(cj, newx, dx=1.0, x0=0)

  Evaluate a quadratic spline at the new set of points.

  Parameters:
    cj ndarray

      Quadratic spline coefficients

    newx ndarray

      New set of points.

    dx float, optional

      Old sample-spacing, the default value is 1.0.

    x0 int, optional

      Old origin, the default value is 0.

  Returns:
    res ndarray

      Evaluated a quadratic spline points.

  See also

  `qspline1d`

    Compute quadratic spline coefficients for rank-1 array.

  Notes

  dx is the old sample-spacing while x0 was the old origin. In other-words the old-sample points (knot-points) for which the cj represent spline coefficients were at equally-spaced points of:

      oldx = x0 + j*dx  j=0...N-1, with N=len(cj)

  Edges are handled using mirror-symmetric boundary conditions.

  Array API Standard Support

  `qspline1d_eval` has experimental support for Python Array API Standard compatible backends in addition to NumPy. Please consider testing these features by setting an environment variable `SCIPY_ARRAY_API=1` and providing CuPy, PyTorch, JAX, or Dask arrays as array arguments. The following combinations of backend and device (or other capability) are supported.

  Library | CPU | GPU
  --- | --- | ---
  NumPy | ✅ | n/a
  CuPy | n/a | ✅
  PyTorch | ✅ | ⛔
  JAX | ⚠️ no JIT | ⛔
  Dask | ⚠️ computes graph | n/a

  See Support for the array API standard for more information.

  Examples

  We can filter a signal to reduce and smooth out high-frequency noise with a quadratic spline:

      >>> import numpy as np
      >>> import matplotlib.pyplot as plt
      >>> from scipy.signal import qspline1d, qspline1d_eval
      >>> rng = np.random.default_rng()
      >>> sig = np.repeat([0., 1., 0.], 100)
      >>> sig += rng.standard_normal(len(sig))*0.05  # add noise
      >>> time = np.linspace(0, len(sig))
      >>> filtered = qspline1d_eval(qspline1d(sig), time)
      >>> plt.plot(sig, label="signal")
      >>> plt.plot(time, filtered, label="filtered")
      >>> plt.legend()
      >>> plt.show()