def test_linear_slope_raises_error(ts_annual_da):
"""Tests that error is raised for `linear_slope` when independent variable is
in y position."""
with pytest.raises(ValueError):
data = ts_annual_da()
x = data['time']
y = data
linear_slope(y, x, 'time')
def test_linear_slope_time_conversion_accurate(ts_annual_da):
"""Tests that computed slope with cftime/datetime conversion is accurate."""
data = ts_annual_da()
data2 = data.copy()
# Just create numeric time, e.g. time in years.
data2['time'] = np.arange(data2.time.size)
slope_cftime = linear_slope(data['time'], data, 'time')
slope_ints = linear_slope(data2['time'], data2, 'time')
diff = slope_cftime - slope_ints
assert np.abs(diff) < 1e-4
def test_linear_slope_linregress_same_result(ts_annual_da):
"""Tests that ``linear_slope`` and ``linregress`` returns the same result
for the slope parameter."""
data = ts_annual_da()
x = data['time']
y = data
m1 = linear_slope(x, y, 'time')
m2 = linregress(x, y, 'time').sel(parameter='slope')
assert np.abs(m1.values - m2.values) < 1e-15