Allow np.timedelta64 inputs to region parameter

Cast np.timedelta64 inputs to int, so that they can be understood by GMT.

pygmt/helpers/decorators.py

@@ -5,6 +5,7 @@
 arguments, insert common text into docstrings, transform arguments to strings,
 etc.
 """
+import datetime
 import functools
 import textwrap
 import warnings
@@ -673,14 +674,19 @@ def kwargs_to_strings(**conversions):
     >>> module(123, bla=(1, 2, 3), foo=True, A=False, i=(5, 6))
     {'A': False, 'bla': (1, 2, 3), 'foo': True, 'i': '5,6'}
     args: 123
+
+    >>> # Test that region accepts arguments with datetime or timedelta type
     >>> import datetime
     >>> module(
     ...     R=[
     ...         np.datetime64("2010-01-01T16:00:00"),
     ...         datetime.datetime(2020, 1, 1, 12, 23, 45),
+    ...         np.timedelta64(0, "h"),
+    ...         np.timedelta64(24, "h"),
     ...     ]
     ... )
-    {'R': '2010-01-01T16:00:00/2020-01-01T12:23:45.000000'}
+    {'R': '2010-01-01T16:00:00/2020-01-01T12:23:45.000000/0/24'}
+
     >>> import pandas as pd
     >>> import xarray as xr
     >>> module(
@@ -690,6 +696,7 @@ def kwargs_to_strings(**conversions):
     ...     ]
     ... )
     {'R': '2005-01-01T08:00:00.000000000/2015-01-01T12:00:00.123456'}
+
     >>> # Here is a more realistic example
     >>> # See https://github.com/GenericMappingTools/pygmt/issues/2361
     >>> @kwargs_to_strings(
@@ -760,14 +767,23 @@ def new_module(*args, **kwargs):
                 if fmt in separators and is_nonstr_iter(value):
                     for index, item in enumerate(value):
                         if " " in str(item):
-                            # Check if there is a space " " when converting
-                            # a pandas.Timestamp/xr.DataArray to a string.
-                            # If so, use np.datetime_as_string instead.
-                            # Convert datetime-like item to ISO 8601
-                            # string format like YYYY-MM-DDThh:mm:ss.ffffff.
-                            value[index] = np.datetime_as_string(
-                                np.asarray(item, dtype=np.datetime64)
-                            )
+                            # Check if there is a space " " in the item, which
+                            # is typically present in objects such as
+                            # np.timedelta64, pd.Timestamp, or xr.DataArray.
+                            # If so, convert the item to a numerical or string
+                            # type that is understood by GMT as follows:
+                            if getattr(
+                                getattr(item, "dtype", ""), "name", ""
+                            ).startswith("timedelta"):
+                                # A np.timedelta64 item is cast to integer
+                                value[index] = item.astype("int")
+                            else:
+                                # A pandas.Timestamp/xr.DataArray containing
+                                # a datetime-like object is cast to ISO 8601
+                                # string format like YYYY-MM-DDThh:mm:ss.ffffff
+                                value[index] = np.datetime_as_string(
+                                    np.asarray(item, dtype=np.datetime64)
+                                )
                     newvalue = separators[fmt].join(f"{item}" for item in value)
                     # Changes in bound.arguments will reflect in bound.args
                     # and bound.kwargs.

pygmt/tests/test_plot.py

@@ -460,7 +460,7 @@ def test_plot_timedelta64():
     fig = Figure()
     fig.basemap(
         projection="X8c/5c",
-        region=[0, 8, 0, 10],
+        region=[np.timedelta64(0, "D"), np.timedelta64(8, "D"), 0, 10],
         frame=["WSne", "xaf+lForecast Days", "yaf+lRMSE"],
     )
     fig.plot(