Minor corrections

pynkowski/data/array.py

@@ -97,8 +97,6 @@ class DataArray(DataField):
  def __init__(self, field, normalise=True, mask=None, spacing=1.):
  dim = len(field.shape)
  super().__init__(field, dim=dim, name='DataArray', mask=mask)
- if field.ndim != 3:
- raise ValueError('The field must be a 3D array')
  if self.mask.shape != self.field.shape:
  raise ValueError('The map and the mask have different shapes')
  if normalise:
@@ -142,12 +140,15 @@ def get_second_der(self):
  - second covariant derivative wrt e₂e₃ in self.second_der[5]
 
  """
+ if self.first_der is None:
+ self.get_first_der()
  self.second_der = np.zeros((self.dim*(self.dim+1)//2, *self.field.shape))
  d = self.dim
  for i in np.arange(self.dim, dtype=int):
  indeces = [i]
  for j in np.arange(i+1, self.dim, dtype=int):
  indeces.append((d*(d-1)/2) - (d-i)*((d-i)-1)/2 + j - i - 1 + d)
+ indeces = np.array(indeces, dtype=int)
  self.second_der[indeces] = np.gradient(self.first_der[i], self.spacing, edge_order=2)[i:d]
 
  def maxima_list(self):