Move sfs.util.displacement() to sfs.fd.displacement()

Closes #30.

Author: mgeier

doc/examples/animations-pulsating-sphere.ipynb

@@ -33,7 +33,7 @@
     "\n",
     "while the last one can be obtained by using\n",
     "\n",
-    "- [sfs.util.displacement()](../sfs.util.rst#sfs.util.displacement)\n",
+    "- [sfs.fd.displacement()](../sfs.fd.rst#sfs.fd.displacement)\n",
     "\n",
     "which converts the particle velocity into displacement.\n",
     "\n",

doc/examples/animations_pulsating_sphere.py

@@ -10,7 +10,7 @@ def particle_displacement(omega, center, radius, amplitude, grid, frames,
     """Generate sound particle animation."""
     velocity = sfs.fd.source.pulsating_sphere_velocity(
                omega, center, radius, amplitude, grid)
-    displacement = sfs.util.displacement(velocity, omega)
+    displacement = sfs.fd.displacement(velocity, omega)
     phasor = np.exp(1j * 2 * np.pi / frames)
 
     fig, ax = plt.subplots(figsize=figsize)

doc/examples/plot_particle_density.py

@@ -19,7 +19,7 @@
 
 def plot_particle_displacement(title):
     # compute displacement
-    X = grid + amplitude * sfs.util.displacement(v, omega)
+    X = grid + amplitude * sfs.fd.displacement(v, omega)
     # plot displacement
     plt.figure(figsize=(15, 15))
     plt.cla()

sfs/fd/__init__.py

@@ -13,6 +13,7 @@
 """
 from . import source
 from .. import array as _array
+from .. import util as _util
 import numpy as _np
 
 
@@ -22,6 +23,17 @@ def shiftphase(p, phase):
     return p * _np.exp(1j * phase)
 
 
+def displacement(v, omega):
+    r"""Particle displacement.
+
+    .. math::
+
+        d(x, t) = \int_{-\infty}^t v(x, \tau) d\tau
+
+    """
+    return _util.as_xyz_components(v) / (1j * omega)
+
+
 def synthesize(d, weights, ssd, secondary_source_function, **kwargs):
     """Compute sound field for a generic driving function.
 

sfs/util.py

@@ -339,17 +339,6 @@ def normalize_vector(x):
     return x / np.linalg.norm(x)
 
 
-def displacement(v, omega):
-    r"""Particle displacement.
-
-    .. math::
-
-        d(x, t) = \int_{-\infty}^t v(x, \tau) d\tau
-
-    """
-    return as_xyz_components(v) / (1j * omega)
-
-
 def db(x, *, power=False):
     """Convert *x* to decibel.