def test_cross_phase_2d(self, dask):
Ny, Nx = (32, 16)
x = np.linspace(0, 1, num=Nx, endpoint=False)
y = np.ones(Ny)
f = 6
phase_offset = np.pi / 2
signal1 = np.cos(2 * np.pi * f * x) # frequency = 1/(2*pi)
signal2 = np.cos(2 * np.pi * f * x - phase_offset)
da1 = xr.DataArray(
data=signal1 * y[:, np.newaxis],
name="a",
dims=["y", "x"],
coords={
"y": y,
"x": x
},
)
da2 = xr.DataArray(
data=signal2 * y[:, np.newaxis],
name="b",
dims=["y", "x"],
coords={
"y": y,
"x": x
},
)
with pytest.raises(ValueError):
xrft.cross_phase(da1, da2, dim=["y", "x"])
if dask:
da1 = da1.chunk({"x": 16})
da2 = da2.chunk({"x": 16})
cp = xrft.cross_phase(da1, da2, dim=["x"])
actual_phase_offset = cp.sel(freq_x=f).values
npt.assert_almost_equal(actual_phase_offset, phase_offset)
def test_cross_phase_true_phase_2d(self, dask):
"""With true_phase = True, a lag on the coordinates should be recovered in cross_phase"""
dx = 0.1
dy = 0.14
x = np.arange(-10, 10, dx)
y = np.arange(-18, 18, dy)
x = xr.DataArray(x, dims="x", coords={"x": x})
y = xr.DataArray(y, dims="y", coords={"y": y})
fx = np.random.choice(np.fft.fftfreq(len(x), dx))
fy = np.random.choice(np.fft.fftfreq(len(y), dy))
da1 = np.cos(2 * np.pi * fx * x + 2 * np.pi * fy * y)
lagx = np.random.rand() * x.max().data
lagy = np.random.rand() * y.max().data
da2 = da1.assign_coords(x=da1["x"] + lagx, y=da1["y"] + lagy)
if dask:
da1 = da1.chunk()
da2 = da2.chunk()
cp = xrft.cross_phase(da1, da2, true_phase=True)
offset = cp[
{
"freq_x": (np.abs(cp["freq_x"] - fx)).argmin(),
"freq_y": (np.abs(cp["freq_y"] - fy)).argmin(),
}
].data
phase_offset = 2 * np.pi * (fx * lagx + fy * lagy)
phase_offset = np.arctan2(
np.sin(phase_offset), np.cos(phase_offset)
) # Offset in [-pi, pi]
npt.assert_almost_equal(np.float(offset), phase_offset)
def test_cross_phase_2d(self, dask):
Ny, Nx = (32, 16)
x = np.linspace(0, 1, num=Nx, endpoint=False)
y = np.ones(Ny)
f = 6
phase_offset = np.pi/2
signal1 = np.cos(2*np.pi*f*x) # frequency = 1/(2*pi)
signal2 = np.cos(2*np.pi*f*x - phase_offset)
da1 = xr.DataArray(data=signal1*y[:,np.newaxis], name='a',
dims=['y','x'], coords={'y':y, 'x':x})
da2 = xr.DataArray(data=signal2*y[:,np.newaxis], name='b',
dims=['y','x'], coords={'y':y, 'x':x})
with pytest.raises(ValueError):
xrft.cross_phase(da1, da2, dim=['y','x'])
if dask:
da1 = da1.chunk({'x': 16})
da2 = da2.chunk({'x': 16})
cp = xrft.cross_phase(da1, da2, dim=['x'])
actual_phase_offset = cp.sel(freq_x=f).values
npt.assert_almost_equal(actual_phase_offset, phase_offset)
def test_cross_phase_1d(self, dask):
N = 32
x = np.linspace(0, 1, num=N, endpoint=False)
f = 6
phase_offset = np.pi / 2
signal1 = np.cos(2 * np.pi * f * x) # frequency = 1/(2*pi)
signal2 = np.cos(2 * np.pi * f * x - phase_offset)
da1 = xr.DataArray(data=signal1, name="a", dims=["x"], coords={"x": x})
da2 = xr.DataArray(data=signal2, name="b", dims=["x"], coords={"x": x})
if dask:
da1 = da1.chunk({"x": 32})
da2 = da2.chunk({"x": 32})
cp = xrft.cross_phase(da1, da2, dim=["x"])
actual_phase_offset = cp.sel(freq_x=f).values
npt.assert_almost_equal(actual_phase_offset, phase_offset)
assert cp.name == "a_b_phase"
xrt.assert_equal(xrft.cross_phase(da1, da2), cp)
with pytest.raises(ValueError):
xrft.cross_phase(da1, da2.isel(x=0).drop("x"))
with pytest.raises(ValueError):
xrft.cross_phase(da1, da2.rename({"x": "y"}))
def test_cross_phase_1d(self, dask):
N = 32
x = np.linspace(0, 1, num=N, endpoint=False)
f = 6
phase_offset = np.pi/2
signal1 = np.cos(2*np.pi*f*x) # frequency = 1/(2*pi)
signal2 = np.cos(2*np.pi*f*x - phase_offset)
da1 = xr.DataArray(data=signal1, name='a', dims=['x'], coords={'x': x})
da2 = xr.DataArray(data=signal2, name='b', dims=['x'], coords={'x': x})
if dask:
da1 = da1.chunk({'x': 32})
da2 = da2.chunk({'x': 32})
cp = xrft.cross_phase(da1, da2, dim=['x'])
actual_phase_offset = cp.sel(freq_x=f).values
npt.assert_almost_equal(actual_phase_offset, phase_offset)
assert cp.name == 'a_b_phase'
xrt.assert_equal(xrft.cross_phase(da1, da2), cp)
with pytest.raises(ValueError):
xrft.cross_phase(da1, da2.isel(x=0).drop('x'))
with pytest.raises(ValueError):
xrft.cross_phase(da1, da2.rename({'x':'y'}))
def test_cross_phase_2d(self, dask):
dx = 0.1
dy = 0.14
x = np.arange(-10, 10, dx)
y = np.arange(-18, 18, dy)
x = xr.DataArray(x, dims="x", coords={"x": x})
y = xr.DataArray(y, dims="y", coords={"y": y})
fx = np.random.choice(np.fft.fftfreq(len(x), dx))
fy = np.random.choice(np.fft.fftfreq(len(y), dy))
phase_offset = 2 * (np.random.rand() - 0.5) * np.pi
da1 = np.cos(2 * np.pi * fx * x + 2 * np.pi * fy * y)
da2 = np.cos(2 * np.pi * fx * x + 2 * np.pi * fy * y - phase_offset)
if dask:
da1 = da1.chunk()
da2 = da2.chunk()
cp = xrft.cross_phase(da1, da2)
offset = cp[{
"freq_x": (np.abs(cp["freq_x"] - fx)).argmin(),
"freq_y": (np.abs(cp["freq_y"] - fy)).argmin(),
}].data
npt.assert_almost_equal(offset, phase_offset)
