BUG: plotting with non-nano TimedeltaIndex

pandas/plotting/_matplotlib/converter.py

@@ -61,6 +61,7 @@
     from matplotlib.axis import Axis
 
     from pandas._libs.tslibs.offsets import BaseOffset
+    from pandas._typing import TimeUnit
 
 
 _mpl_units: dict = {}  # Cache for units overwritten by us
@@ -1099,18 +1100,22 @@ class TimeSeries_TimedeltaFormatter(mpl.ticker.Formatter):  # pyright: ignore[re
     Formats the ticks along an axis controlled by a :class:`TimedeltaIndex`.
     """
 
+    def __init__(self, unit: TimeUnit = "ns"):
+        self.unit = unit
+        super().__init__()
+
     axis: Axis
 
     @staticmethod
-    def format_timedelta_ticks(x, pos, n_decimals: int) -> str:
+    def format_timedelta_ticks(x, pos, n_decimals: int, exp: int) -> str:
         """
         Convert seconds to 'D days HH:MM:SS.F'
         """
-        s, ns = divmod(x, 10**9)  # TODO(non-nano): this looks like it assumes ns
+        s, ns = divmod(x, 10**exp)
         m, s = divmod(s, 60)
         h, m = divmod(m, 60)
         d, h = divmod(h, 24)
-        decimals = int(ns * 10 ** (n_decimals - 9))
+        decimals = int(ns * 10 ** (n_decimals - exp))
         s = f"{int(h):02d}:{int(m):02d}:{int(s):02d}"
         if n_decimals > 0:
             s += f".{decimals:0{n_decimals}d}"
@@ -1119,6 +1124,7 @@ def format_timedelta_ticks(x, pos, n_decimals: int) -> str:
         return s
 
     def __call__(self, x, pos: int | None = 0) -> str:
+        exp = {"ns": 9, "us": 6, "ms": 3, "s": 0}[self.unit]
         (vmin, vmax) = tuple(self.axis.get_view_interval())
-        n_decimals = min(int(np.ceil(np.log10(100 * 10**9 / abs(vmax - vmin)))), 9)
-        return self.format_timedelta_ticks(x, pos, n_decimals)
+        n_decimals = min(int(np.ceil(np.log10(100 * 10**exp / abs(vmax - vmin)))), exp)
+        return self.format_timedelta_ticks(x, pos, n_decimals, exp)

pandas/plotting/_matplotlib/timeseries.py

@@ -341,7 +341,7 @@ def format_dateaxis(
         subplot.format_coord = functools.partial(_format_coord, freq)
 
     elif isinstance(index, ABCTimedeltaIndex):
-        subplot.xaxis.set_major_formatter(TimeSeries_TimedeltaFormatter())
+        subplot.xaxis.set_major_formatter(TimeSeries_TimedeltaFormatter(index.unit))
     else:
         raise TypeError("index type not supported")
 

pandas/tests/plotting/test_converter.py

@@ -347,7 +347,7 @@ class TestTimeDeltaConverter:
     )
     def test_format_timedelta_ticks(self, x, decimal, format_expected):
         tdc = converter.TimeSeries_TimedeltaFormatter
-        result = tdc.format_timedelta_ticks(x, pos=None, n_decimals=decimal)
+        result = tdc.format_timedelta_ticks(x, pos=None, n_decimals=decimal, exp=9)
         assert result == format_expected
 
     @pytest.mark.parametrize("view_interval", [(1, 2), (2, 1)])

pandas/tests/plotting/test_datetimelike.py

@@ -1531,7 +1531,7 @@ def test_format_timedelta_ticks_narrow(self):
         assert len(result_labels) == len(expected_labels)
         assert result_labels == expected_labels
 
-    def test_format_timedelta_ticks_wide(self):
+    def test_format_timedelta_ticks_wide(self, unit):
         expected_labels = [
             "00:00:00",
             "1 days 03:46:40",
@@ -1544,7 +1544,7 @@ def test_format_timedelta_ticks_wide(self):
             "9 days 06:13:20",
         ]
 
-        rng = timedelta_range("0", periods=10, freq="1 D")
+        rng = timedelta_range("0", periods=10, freq="1 D", unit=unit)
         df = DataFrame(np.random.default_rng(2).standard_normal((len(rng), 3)), rng)
         _, ax = mpl.pyplot.subplots()
         ax = df.plot(fontsize=2, ax=ax)