More sensible time axis and tick labels for 2D plots (SciTools#5561)

* Don't used mpl date2num

* removed units for time coords due to not matching autoticks

* update imagerepo.json

* Revert change from SciTools#616, as this is now handled within _title

* whatsnew

* update test data version

---------

Co-authored-by: alex chamberlain-clay <a.chamberlain-clay@metoffice.gov.uk>

.github/workflows/benchmarks_run.yml

@@ -29,7 +29,7 @@ jobs:
     env:
       IRIS_TEST_DATA_LOC_PATH: benchmarks
       IRIS_TEST_DATA_PATH: benchmarks/iris-test-data
-      IRIS_TEST_DATA_VERSION: "2.21"
+      IRIS_TEST_DATA_VERSION: "2.22"
       # Lets us manually bump the cache to rebuild
       ENV_CACHE_BUILD: "0"
       TEST_DATA_CACHE_BUILD: "2"

.github/workflows/ci-tests.yml

@@ -50,7 +50,7 @@ jobs:
             session: "tests"
 
     env:
-      IRIS_TEST_DATA_VERSION: "2.21"
+      IRIS_TEST_DATA_VERSION: "2.22"
       ENV_NAME: "ci-tests"
 
     steps:

docs/src/whatsnew/latest.rst

@@ -48,6 +48,9 @@ This document explains the changes made to Iris for this release
 #. `@ESadek-MO`_ has updated :mod:`iris.tests.graphics.idiff` to stop duplicated file names
    preventing acceptance. (:issue:`5098`, :pull:`5482`)
 
+#. `@acchamber`_ and `@rcomer`_ modified 2D plots so that time axes and their
+   ticks have more sensible default labels.  (:issue:`5426`, :pull:`5561`)
+
 
 💣 Incompatible Changes
 =======================

lib/iris/plot.py

@@ -22,7 +22,6 @@
 import matplotlib.animation as animation
 import matplotlib.axes
 import matplotlib.collections as mpl_collections
-import matplotlib.dates as mpl_dates
 from matplotlib.offsetbox import AnchoredText
 import matplotlib.pyplot as plt
 import matplotlib.ticker as mpl_ticker
@@ -454,10 +453,6 @@ def _draw_2d_from_bounds(draw_method_name, cube, *args, **kwargs):
                 else:
                     values = coord.contiguous_bounds()
                     values = _fixup_dates(coord, values)
-                    if values.dtype == np.dtype(object) and isinstance(
-                        values[0], datetime.datetime
-                    ):
-                        values = mpl_dates.date2num(values)
 
             plot_arrays.append(values)
 
@@ -557,10 +552,6 @@ def _draw_2d_from_points(draw_method_name, arg_func, cube, *args, **kwargs):
                     )
                 plot_arrays.append(np.arange(values.size))
                 string_axes[axis_name] = values
-            elif values.dtype == np.dtype(object) and isinstance(
-                values[0], datetime.datetime
-            ):
-                plot_arrays.append(mpl_dates.date2num(values))
             else:
                 plot_arrays.append(values)
 

lib/iris/quickplot.py

@@ -14,9 +14,7 @@
 """
 
 import cf_units
-from matplotlib import __version__ as _mpl_version
 import matplotlib.pyplot as plt
-from packaging import version
 
 import iris.config
 import iris.coords
@@ -44,18 +42,11 @@ def _title(cube_or_coord, with_units):
             units.is_unknown()
             or units.is_no_unit()
             or units == cf_units.Unit("1")
+            or units.is_time_reference()
         ):
             if _use_symbol(units):
                 units = units.symbol
-            elif units.is_time_reference():
-                # iris.plot uses matplotlib.dates.date2num, which is fixed to the below unit.
-                if version.parse(_mpl_version) >= version.parse("3.3"):
-                    days_since = "1970-01-01"
-                else:
-                    days_since = "0001-01-01"
-                units = "days since {}".format(days_since)
             title += " / {}".format(units)
-
     return title
 
 
@@ -117,10 +108,8 @@ def _label_with_points(cube, result=None, ndims=2, coords=None, axes=None):
 def _get_titles(u_object, v_object):
     if u_object is None:
         u_object = iplt._u_object_from_v_object(v_object)
-    xunits = u_object is not None and not u_object.units.is_time_reference()
-    yunits = not v_object.units.is_time_reference()
-    xlabel = _title(u_object, with_units=xunits)
-    ylabel = _title(v_object, with_units=yunits)
+    xlabel = _title(u_object, with_units=True)
+    ylabel = _title(v_object, with_units=True)
     title = ""
     if u_object is None:
         title = _title(v_object, with_units=False)

lib/iris/tests/results/imagerepo.json

@@ -129,8 +129,8 @@
     "iris.tests.test_plot.TestHybridHeight.test_points.3": "fe857b91917a847ec4bd3f01c47c6ca43b11915a3ea4db3b1b4a84c4c03f3fc1",
     "iris.tests.test_plot.TestHybridHeight.test_points.4": "b878387e978ec2f0c0f09f83878f3f81c070c0fe78d0c1763fa13856d03e3f0f",
     "iris.tests.test_plot.TestMissingCS.test_missing_cs.0": "fa816ac1857e853cc17e957ac15f3e8494c6c8f43e81c13b3f813e91c07e3f46",
-    "iris.tests.test_plot.TestMissingCoord.test_no_u.0": "ea856a95955a954ac17f954a807e3f48951ac07e3f81c0ff7ea16a81c0bf3f81",
-    "iris.tests.test_plot.TestMissingCoord.test_no_u.1": "ea956ab5954a954ac17e9542817f2f60950ac07f3e80c0ff7a856aa5c2ff3f80",
+    "iris.tests.test_plot.TestMissingCoord.test_no_u.0": "ea856a95955a956ac17f954a817e3f8c953ac07e3e81c07f7ea16a81c07e3e81",
+    "iris.tests.test_plot.TestMissingCoord.test_no_u.1": "ea956ab5954a954ac17e954a857f3f80954ac07f7e80c07f7a856a84c07f3f81",
     "iris.tests.test_plot.TestMissingCoord.test_no_v.0": "fa816a85957a857ac17e954ac17e1fa2950bc07e3e81c07f3e807a85c17f3f81",
     "iris.tests.test_plot.TestMissingCoord.test_no_v.1": "fa856a85957a857ac17e954ac17e9d02954ac07e3e81c07f3e857a85c2fd3f80",
     "iris.tests.test_plot.TestMissingCoord.test_none.0": "fa816a85957a857ac17e954ac17e3fa2950ac07e3e80c07f3e807a85c1ff3f81",
@@ -168,12 +168,12 @@
     "iris.tests.test_plot.TestPlotCitation.test_axes.0": "abf895467a1d9506f811783485437abd85427ab995067ab9f00687f96afe87c8",
     "iris.tests.test_plot.TestPlotCitation.test_figure.0": "abf895467a1d9506f811783485437abd85427ab995067ab9f00687f96afe87c8",
     "iris.tests.test_plot.TestPlotCoordinatesGiven.test_non_cube_coordinate.0": "fa81857e857e3e85857e7a81857e7a81857e7a817e81780b7a81c56a7a81857e",
-    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.0": "ea853f10956ac1e1957a854e957a207e955e6aa76ae17aa16a856aaf6ab19e12",
-    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.1": "ea853a85857a857a957a857a957ed05a857b3e946a606b917a816f247a853af4",
-    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.2": "eafdcec9f4219530b696a56694c3852a95656b7b85986acdc06516adad186e9a",
-    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.3": "aff24ab7fd05952dbd0f950f910fed48c47868f2e1b9329094266e345a850f6c",
-    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.4": "eaa9b5699556854e9456854ed05625f9d0a92bfdc0a90afd81f97e00855e7ab6",
-    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.5": "eaf73e0d9503852c950395ac9528c1fad06cc0f2d1ec6af2c0fc6a536a1797f3",
+    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.0": "ea853e11956ac1e3957a844e957a607e955e6ae36ae17aa16a856be86ab13c32",
+    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.1": "ea857a85857ac57a957a857a957ad05e850b3ed46e206b917a816f247a953ae4",
+    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.2": "ebfdcac9bd209434b696856795cb012e95676b7b81186acdc06536ad89182fda",
+    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.3": "aaff7ab2fd04902cfd0c950f9d010f4bd64069f3e1993a9894262e345ae56f6c",
+    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.4": "eaa9d5129556c55695568556955623f9c0292bf9c0a90bfdc0fd7e0085562ff9",
+    "iris.tests.test_plot.TestPlotCoordinatesGiven.test_tx.5": "eaf77a0d9553c52c950095ac952885ea952c87f3952c6bf3d42c6a536a57bf80",
     "iris.tests.test_plot.TestPlotCoordinatesGiven.test_x.0": "afea950ddb13c03e34359ad8a4c86f24913f2693806e3ff1f4087b4285fd2af2",
     "iris.tests.test_plot.TestPlotCoordinatesGiven.test_y.0": "afee9632de05c9d9f180d168c454a53e931b3e84954a3b8c85f94ce703ff7284",
     "iris.tests.test_plot.TestPlotCoordinatesGiven.test_yx.0": "ea853f00957ac07c957ac0bf951a69f3c47c7a5f3a4127816b953e646b813761",
@@ -202,8 +202,8 @@
     "iris.tests.test_plot.TestQuickplotPlot.test_x.0": "82ff950b7f81c0d6620199bcfc5e986695734da1816e1b2c85be2b65d96276d1",
     "iris.tests.test_plot.TestQuickplotPlot.test_y.0": "a2fbb46e7f10c99f2013d863e46498dcd06c0d2798421fa5dd221e7789ff6f10",
     "iris.tests.test_plot.TestQuickplotPlot.test_z.0": "a3ffc1de7e009c7030019786f438cde3810fd93c9b734a778ce47c9799b02731",
-    "iris.tests.test_plot.TestSimple.test_bounds.0": "ea856a85954a957ac17e954ac17a9d3a956ac07e3e80c07f3e857aa5c27d3f80",
-    "iris.tests.test_plot.TestSimple.test_points.0": "ea856a85957a957ac17e954ac17e1ea2950bc07e3e80c07f3e807a85c1ff3f81",
+    "iris.tests.test_plot.TestSimple.test_bounds.0": "ea856a85955a957ac17e954ac17a9d22956ac07e3e81c07f3e857aa5c27d3f80",
+    "iris.tests.test_plot.TestSimple.test_points.0": "ea856a85957a957ac17e954ac17e1fa2950ac07e3e80c07d3e847a85c1ff3f81",
     "iris.tests.test_plot.TestSymbols.test_cloud_cover.0": "eb5291e494ad6e136b5291ec94ad6e136b5291ec94ad6e136b5291ec94ad6e13",
     "iris.tests.test_quickplot.TestLabels.test_alignment.0": "be813fe0954ac07fc0ff3e81c03fc97a6d0094af3f80c17f36a53240d97f2d82",
     "iris.tests.test_quickplot.TestLabels.test_contour.0": "a7fd955a7a016d1a3217c962e4819a56c96f3c859b624d2584de3a6999b662db",
@@ -220,12 +220,12 @@
     "iris.tests.test_quickplot.TestPlotHist.test_horizontal.0": "b59cc3dadb433c24c4f166039438793591a7dbdcbcdc9ccc68c697a91b139131",
     "iris.tests.test_quickplot.TestPlotHist.test_vertical.0": "bf80c7c6c07d7959647e343a33364b699589c6c64ec0312b9e227ad681ffcc68",
     "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_non_cube_coordinate.0": "fe816a85857a957ac07f957ac07f3e80956ac07f3e80c07f3e813e85c07e3f80",
-    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.0": "ea856a95955a956ac17f950a807e3f4e951ac07e3f81c0ff3ea16aa1c0bd3e81",
-    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.1": "ea856a85957a957ac17e954ac17e1ea2950bc07e3e80c07f3e807a85c1ff3f81",
-    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.2": "eaf9eec9f729943032168d66d4db896e9567497b81304aedc96514ad8d18669a",
-    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.3": "a6fb4b967f00950eb00f9d0f900fcd62dc7868f2c1bb3a909c266e34daa52f6c",
-    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.4": "eaa9b549f756854ea0168d6ed556896fd8a909ed88290afdd9e97e008d6e2296",
-    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.5": "aad73e0df78085ac840195ac9528d9fad56cd8f2906c48f2d0ec7a536a1737f3",
+    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.0": "ea856a95955a956ac17f950a817e3fcc951ac07e3e81c07f7ea16a85c07e3e81",
+    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.1": "ea856a85957a957ac17e954ac17e1fa2950ac07e3e80c07d3e847a85c1ff3f81",
+    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.2": "eaf9e2c9ff60b43036168d6795c2892e95674b7b80304aedc8651ead99192eda",
+    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.3": "a2ff7892771d912cb4089d0ffd4b8d429c4049f3d1bb1a909c266e34dae56f68",
+    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.4": "eaa9f598b756a41e8056855e955689f9d9610be988290bfdd9fdfe0089562a61",
+    "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_tx.5": "ead7780cf7d3c5acb40095acd56999e2952899f2d5ec0bf3902c6a536a57b700",
     "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_x.0": "a6fb958dff50c03e203598dca4c9cd26933f9cf3886e1de1dc047b4289ec2672",
     "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_y.0": "a2ffb6127f0dc9992085d960c6748d3edb121ca49d6a1b048df34ce789ff7205",
     "iris.tests.test_quickplot.TestQuickplotCoordinatesGiven.test_yx.0": "ea856a95957a957ac07e954ac17e3e86950bc17f3ea4c27d3e833ac1c1e03f80",