Calendar conversion

HISTORY.rst

@@ -2,6 +2,10 @@
 History
 =======
 
+0.17.x
+------
+* Added `convert_calendar` and `interp_calendar` to help in the conversion between calendars.
+
 0.16.0 (2020-04-23)
 -------------------
 * Added `vectorize` flag to `subset_shape` and `create_mask_vectorize` function based on `shapely.vectorize` as default backend for mask creation.

tests/conftest.py

@@ -5,7 +5,7 @@
 import pytest
 import xarray as xr
 
-from xclim.core.calendar import calendars
+from xclim.core.calendar import max_doy
 
 
 @pytest.fixture
@@ -151,7 +151,7 @@ def ndq_series():
 @pytest.fixture
 def per_doy():
     def _per_doy(values, calendar="standard", units="kg m-2 s-1"):
-        n = calendars[calendar]
+        n = max_doy[calendar]
         if len(values) != n:
             raise ValueError(
                 "Values must be same length as number of days in calendar."

tests/test_calendar.py

@@ -8,7 +8,13 @@
 from xarray.coding.cftimeindex import CFTimeIndex
 
 from xclim.core.calendar import adjust_doy_calendar
-from xclim.core.calendar import infer_doy_max
+from xclim.core.calendar import convert_calendar
+from xclim.core.calendar import datetime_to_decimal_year
+from xclim.core.calendar import days_in_year
+from xclim.core.calendar import ensure_cftime_array
+from xclim.core.calendar import get_calendar
+from xclim.core.calendar import interp_calendar
+from xclim.core.calendar import max_doy
 from xclim.core.calendar import percentile_doy
 from xclim.core.calendar import time_bnds
 
@@ -40,6 +46,12 @@ def da(index):
     )
 
 
+def date_range(*args, calendar="default", **kwargs):
+    if calendar == "default":
+        return pd.date_range(*args, **kwargs)
+    return xr.cftime_range(*args, calendar=calendar, **kwargs)
+
+
 @pytest.mark.parametrize(
     "freq", ["3A-MAY", "5Q-JUN", "7M", "6480H", "302431T", "23144781S"]
 )
@@ -62,44 +74,228 @@ def test_time_bnds(freq, datetime_index, cftime_index):
     assert_array_equal(cftime_ends, datetime_ends)
 
 
-def test_percentile_doye(tas_series):
+def test_percentile_doy(tas_series):
     tas = tas_series(np.arange(365), start="1/1/2001")
     tas = xr.concat((tas, tas), "dim0")
     p1 = percentile_doy(tas, window=5, per=0.5)
     assert p1.sel(dayofyear=3, dim0=0).data == 2
     assert p1.attrs["units"] == "K"
 
 
-class TestAdjustDoyCalendar:
-    def test_360_to_366(self):
-        source = xr.DataArray(
-            np.arange(360), coords=[np.arange(1, 361)], dims="dayofyear"
-        )
-        time = pd.date_range("2000-01-01", "2001-12-31", freq="D")
-        target = xr.DataArray(np.arange(len(time)), coords=[time], dims="time")
+def test_adjust_doy_360_to_366():
+    source = xr.DataArray(np.arange(360), coords=[np.arange(1, 361)], dims="dayofyear")
+    time = pd.date_range("2000-01-01", "2001-12-31", freq="D")
+    target = xr.DataArray(np.arange(len(time)), coords=[time], dims="time")
 
-        out = adjust_doy_calendar(source, target)
+    out = adjust_doy_calendar(source, target)
 
-        assert out.sel(dayofyear=1) == source.sel(dayofyear=1)
-        assert out.sel(dayofyear=366) == source.sel(dayofyear=360)
+    assert out.sel(dayofyear=1) == source.sel(dayofyear=1)
+    assert out.sel(dayofyear=366) == source.sel(dayofyear=360)
 
-    def test_infer_doy_max(self):
-        fn = os.path.join(
-            TESTS_DATA,
-            "CanESM2_365day",
-            "pr_day_CanESM2_rcp85_r1i1p1_na10kgrid_qm-moving-50bins-detrend_2095.nc",
-        )
-        with xr.open_dataset(fn) as ds:
-            assert infer_doy_max(ds) == 365
 
-        fn = os.path.join(
-            TESTS_DATA,
-            "HadGEM2-CC_360day",
-            "pr_day_HadGEM2-CC_rcp85_r1i1p1_na10kgrid_qm-moving-50bins-detrend_2095.nc",
+@pytest.mark.parametrize(
+    "file,cal,maxdoy",
+    [
+        (
+            (
+                "CanESM2_365day",
+                "pr_day_CanESM2_rcp85_r1i1p1_na10kgrid_qm-moving-50bins-detrend_2095.nc",
+            ),
+            "noleap",
+            365,
+        ),
+        (
+            (
+                "HadGEM2-CC_360day",
+                "pr_day_HadGEM2-CC_rcp85_r1i1p1_na10kgrid_qm-moving-50bins-detrend_2095.nc",
+            ),
+            "360_day",
+            360,
+        ),
+        (("NRCANdaily", "nrcan_canada_daily_pr_1990.nc"), "default", 366),
+    ],
+)
+def test_get_calendar(file, cal, maxdoy):
+    with xr.open_dataset(os.path.join(TESTS_DATA, *file)) as ds:
+        out_cal = get_calendar(ds)
+        assert cal == out_cal
+        assert max_doy[cal] == maxdoy
+
+
+@pytest.mark.parametrize(
+    "source,target,target_as_str,freq",
+    [
+        ("standard", "noleap", True, "D"),
+        ("noleap", "default", True, "D"),
+        ("noleap", "all_leap", False, "D"),
+        ("proleptic_gregorian", "noleap", False, "4H"),
+        ("default", "noleap", True, "4H"),
+    ],
+)
+def test_convert_calendar(source, target, target_as_str, freq):
+    src = xr.DataArray(
+        date_range("2004-01-01", "2004-12-31", freq=freq, calendar=source),
+        dims=("time",),
+        name="time",
+    )
+    da_src = xr.DataArray(
+        np.linspace(0, 1, src.size), dims=("time",), coords={"time": src}
+    )
+    tgt = xr.DataArray(
+        date_range("2004-01-01", "2004-12-31", freq=freq, calendar=target),
+        dims=("time",),
+        name="time",
+    )
+
+    conv = convert_calendar(da_src, target if target_as_str else tgt)
+
+    assert get_calendar(conv) == target
+
+    if target_as_str and max_doy[source] < max_doy[target]:
+        assert conv.size == src.size
+    elif not target_as_str:
+        assert conv.size == tgt.size
+
+        assert conv.isnull().sum() == max(max_doy[target] - max_doy[source], 0)
+
+
+@pytest.mark.parametrize(
+    "source,target,freq",
+    [
+        ("standard", "360_day", "D"),
+        ("360_day", "default", "D"),
+        ("proleptic_gregorian", "360_day", "4H"),
+    ],
+)
+@pytest.mark.parametrize("align_on", ["date", "year"])
+def test_convert_calendar_360_days(source, target, freq, align_on):
+    src = xr.DataArray(
+        date_range("2004-01-01", "2004-12-30", freq=freq, calendar=source),
+        dims=("time",),
+        name="time",
+    )
+    da_src = xr.DataArray(
+        np.linspace(0, 1, src.size), dims=("time",), coords={"time": src}
+    )
+
+    conv = convert_calendar(da_src, target, align_on=align_on)
+
+    assert get_calendar(conv) == target
+
+    if align_on == "date":
+        np.testing.assert_array_equal(
+            conv.time.resample(time="M").last().dt.day,
+            [30, 29, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30],
+        )
+    elif target == "360_day":
+        np.testing.assert_array_equal(
+            conv.time.resample(time="M").last().dt.day,
+            [30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 29],
+        )
+    else:
+        np.testing.assert_array_equal(
+            conv.time.resample(time="M").last().dt.day,
+            [30, 29, 30, 30, 31, 30, 30, 31, 30, 31, 29, 31],
         )
-        with xr.open_dataset(fn) as ds:
-            assert infer_doy_max(ds) == 360
+    if source == "360_day" and align_on == "year":
+        assert conv.size == 360 if freq == "D" else 360 * 4
+    else:
+        assert conv.size == 359 if freq == "D" else 359 * 4
+
+
+@pytest.mark.parametrize(
+    "source,target",
+    [
+        ("standard", "noleap"),
+        ("noleap", "default"),
+        ("standard", "360_day"),
+        ("360_day", "gregorian"),
+        ("noleap", "all_leap"),
+        ("360_day", "noleap"),
+    ],
+)
+def test_interp_calendar(source, target):
+    src = xr.DataArray(
+        date_range("2004-01-01", "2004-07-30", freq="D", calendar=source),
+        dims=("time",),
+        name="time",
+    )
+    tgt = xr.DataArray(
+        date_range("2004-01-01", "2004-07-30", freq="D", calendar=target),
+        dims=("time",),
+        name="time",
+    )
+    da_src = xr.DataArray(
+        np.linspace(0, 1, src.size), dims=("time",), coords={"time": src}
+    )
+    conv = interp_calendar(da_src, tgt)
+
+    assert conv.size == tgt.size
+    assert get_calendar(conv) == target
+
+    np.testing.assert_almost_equal(conv.max(), 1, 2)
+    assert conv.min() == 0
 
-        fn = os.path.join(TESTS_DATA, "NRCANdaily", "nrcan_canada_daily_pr_1990.nc")
-        with xr.open_dataset(fn) as ds:
-            assert infer_doy_max(ds) == 366
+
+@pytest.mark.parametrize(
+    "inp,calout",
+    [
+        (
+            xr.DataArray(
+                date_range("2004-01-01", "2004-01-10", freq="D"),
+                dims=("time",),
+                name="time",
+            ),
+            "gregorian",
+        ),
+        (date_range("2004-01-01", "2004-01-10", freq="D"), "gregorian"),
+        (
+            xr.DataArray(date_range("2004-01-01", "2004-01-10", freq="D")).values,
+            "gregorian",
+        ),
+        (date_range("2004-01-01", "2004-01-10", freq="D"), "gregorian"),
+        (date_range("2004-01-01", "2004-01-10", freq="D", calendar="julian"), "julian"),
+    ],
+)
+def test_ensure_cftime_array(inp, calout):
+    out = ensure_cftime_array(inp)
+    assert out[0].calendar == calout
+
+
+@pytest.mark.parametrize(
+    "year,calendar,exp",
+    [
+        (2004, "standard", 366),
+        (2004, "noleap", 365),
+        (2004, "all_leap", 366),
+        (1500, "default", 365),
+        (1500, "gregorian", 366),
+        (1500, "proleptic_gregorian", 365),
+        (2030, "360_day", 360),
+    ],
+)
+def test_days_in_year(year, calendar, exp):
+    assert days_in_year(year, calendar) == exp
+
+
+@pytest.mark.parametrize(
+    "source_cal, exp180",
+    [
+        ("standard", 0.49180328),
+        ("default", 0.49180328),
+        ("noleap", 0.49315068),
+        ("all_leap", 0.49180328),
+        ("360_day", 0.5),
+        (None, 0.49180328),
+    ],
+)
+def test_datetime_to_decimal_year(source_cal, exp180):
+    times = xr.DataArray(
+        date_range(
+            "2004-01-01", "2004-12-30", freq="D", calendar=source_cal or "default"
+        ),
+        dims=("time",),
+        name="time",
+    )
+    decy = datetime_to_decimal_year(times, calendar=source_cal)
+    np.testing.assert_almost_equal(decy[180] - 2004, exp180)