import numpy as np
[docs]
def add_halo(data, halo=1, halo_value=None):
"""Add a halo of no data value to data.
Parameters
----------
data : array-like
Array to add the halo to.
halo : int, optional
The size of the halo.
halo_value : float, optional
Value to fill the halo with. If not provided, the new data will is not
initialized.
Examples
--------
>>> import numpy as np
>>> from landlab.utils import add_halo
>>> data = np.array([[1, 2, 3], [4, 5, 6]])
>>> add_halo(data, halo_value=9)
array([[9, 9, 9, 9, 9], [9, 1, 2, 3, 9], [9, 4, 5, 6, 9], [9, 9, 9, 9, 9]])
"""
if halo < 0:
raise ValueError("halo must be greater than or equal to zero")
elif halo == 0:
return data.copy()
data_with_halo = np.empty([dim + 2 * halo for dim in data.shape], dtype=data.dtype)
data_with_halo[halo:-halo, halo:-halo] = data
if halo_value is not None:
data_with_halo[:halo, :] = halo_value
data_with_halo[-halo:, :] = halo_value
data_with_halo[:, :halo] = halo_value
data_with_halo[:, -halo:] = halo_value
return data_with_halo