Add additional functions for working with dekads.

CHANGES.md

@@ -1,3 +1,7 @@
+# v0.6.5, 2017-07-10
+
+* Add additonal functions for working with dekads.
+
 # v0.6.4, 2017-06-02
 
 * Refactor resampling routine to be more modular and better usable outside of pytesmo.

pytesmo/timedate/dekad.py

@@ -140,6 +140,79 @@ def check_dekad(date):
     return new_date
 
 
+def dekad_startdate_from_date(dt_in):
+    """
+    dekadal startdate that a date falls in
+
+    Parameters
+    ----------
+    run_dt: datetime.datetime
+
+    Returns
+    -------
+    startdate: datetime.datetime
+        startdate of dekad
+    """
+    if dt_in.day <= 10:
+        startdate = datetime(dt_in.year,
+                             dt_in.month,
+                             1, 0, 0, 0)
+    if dt_in.day >= 11 and dt_in.day <= 20:
+        startdate = datetime(dt_in.year,
+                             dt_in.month,
+                             11, 0, 0, 0)
+    if dt_in.day >= 21:
+        startdate = datetime(dt_in.year,
+                             dt_in.month,
+                             21, 0, 0, 0)
+    return startdate
+
+
+def check_dekad_enddate(dt):
+    """
+    Check if a date is a dekad enddate
+    """
+    return check_dekad(dt) == dt
+
+
+def check_dekad_startdate(dt):
+    """
+    Check if a date is a dekad startdate
+    """
+    if dt.day in [1, 11, 21]:
+        return True
+    else:
+        return False
+
+
+def group_into_dekads(dates, use_dekad_startdate=False):
+    """
+    Group a list of dates into dekads.
+
+    Parameters
+    ----------
+    dates: list of datetime.datetime
+    use_dekad_startdates: boolean, optional
+        If set the dekad reference dates will
+        be the startdates of the dekad
+
+    Returns
+    -------
+    groups: dict
+        keys: dekad reference dates
+        values: list of dates belonging to dekad
+    """
+    groups = {}
+    for dt in dates:
+        dekad_date = check_dekad(dt)
+        if use_dekad_startdate:
+            dekad_date = dekad_startdate_from_date(dekad_date)
+        if dekad_date not in groups:
+            groups[dekad_date] = []
+        groups[dekad_date].append(dt)
+    return groups
+
+
 def dekad2day(year, month, dekad):
     """Gets the day of a dekad.
 

tests/test_timedate/test_dekad.py

@@ -129,6 +129,48 @@ def test_get_dekad_period(self):
     def test_runningdekad2date(self):
         assert dk.runningdekad2date(2014, 35) == datetime(2014, 12, 20)
 
+
+def test_check_dekad_startdate():
+    assert dk.check_dekad_startdate(datetime(2000, 1, 1))
+    assert dk.check_dekad_startdate(datetime(2000, 1, 11))
+    assert dk.check_dekad_startdate(datetime(2000, 1, 21))
+    assert not dk.check_dekad_startdate(datetime(2000, 1, 22))
+
+
+def test_check_dekad_enddate():
+    assert dk.check_dekad_enddate(datetime(2000, 1, 10))
+    assert dk.check_dekad_enddate(datetime(2000, 1, 20))
+    assert dk.check_dekad_enddate(datetime(2000, 1, 31))
+    assert dk.check_dekad_enddate(datetime(2000, 2, 29))
+    assert not dk.check_dekad_enddate(datetime(2000, 2, 28))
+
+
+def test_dekad_startdate_from_date():
+    assert datetime(2000, 1, 1) == dk.dekad_startdate_from_date(
+        datetime(2000, 1, 10))
+    assert datetime(2000, 2, 21) == dk.dekad_startdate_from_date(
+        datetime(2000, 2, 29))
+    assert datetime(2000, 2, 11) == dk.dekad_startdate_from_date(
+        datetime(2000, 2, 17))
+
+
+def test_group_into_dekads():
+    dtimes = [datetime(2000, 1, 10),
+              datetime(2000, 1, 11),
+              datetime(2000, 1, 12),
+              datetime(2000, 1, 23)]
+    groups = dk.group_into_dekads(dtimes)
+    assert groups == {datetime(2000, 1, 10): [datetime(2000, 1, 10)],
+                      datetime(2000, 1, 20): [datetime(2000, 1, 11),
+                                              datetime(2000, 1, 12)],
+                      datetime(2000, 1, 31): [datetime(2000, 1, 23)]}
+    groups = dk.group_into_dekads(dtimes,
+                                  use_dekad_startdate=True)
+    assert groups == {datetime(2000, 1, 1): [datetime(2000, 1, 10)],
+                      datetime(2000, 1, 11): [datetime(2000, 1, 11),
+                                              datetime(2000, 1, 12)],
+                      datetime(2000, 1, 21): [datetime(2000, 1, 23)]}
+
 if __name__ == "__main__":
     # import sys;sys.argv = ['', 'Test.testName']
     unittest.main()