Merge pull request #1660 from astrofrog/slider-format-function

Factor out code to find minimal format for set of values

CHANGES.md

@@ -47,7 +47,7 @@ v0.13.0 (unreleased)
 
 * Improve the display of data cube slice labels to include only the
   precision required given the separation of world coordinate values.
-  [#1500]
+  [#1500, #1660]
 
 * Removed the ability to edit the marker symbol in the style dialog
   since this isn't recognized by any viewer anymore. [#1560]

glue/utils/array.py

@@ -13,7 +13,7 @@
 __all__ = ['unique', 'shape_to_string', 'view_shape', 'stack_view',
            'coerce_numeric', 'check_sorted', 'broadcast_to', 'unbroadcast',
            'iterate_chunks', 'combine_slices', 'nanmean', 'nanmedian', 'nansum',
-           'nanmin', 'nanmax']
+           'nanmin', 'nanmax', 'format_minimal']
 
 
 def unbroadcast(array):
@@ -369,5 +369,24 @@ def nanmax(array, axis=None):
     return bt.nanmax(array, axis=axis)
 
 
-array = np.random.random((2, 5, 4, 2, 3))
-nanmean(array, axis=(1, 2))
+def format_minimal(values):
+    """
+    Find the shortest format that can be used to represent all values in an
+    array such that all the string representations are different.
+
+    The current implementation is not incredibly efficient, but it takes only
+    ~30ms for a 1000 element array and 200ms for a 10000 element array. One
+    could probably make a more efficient implementation but this is good enough
+    for now for what we use it for.
+    """
+    values = np.asarray(values)
+    if np.max(np.abs(values)) > 1e5 or np.min(np.diff(values)) < 1e-5:
+        fmt_type = 'e'
+    else:
+        fmt_type = 'f'
+    for ndec in range(1, 15):
+        fmt = '{{:.{0}{1}}}'.format(ndec, fmt_type)
+        strings = [fmt.format(x) for x in values]
+        if len(strings) == len(set(strings)):
+            break
+    return fmt, strings

glue/utils/tests/test_array.py

@@ -11,7 +11,8 @@
 
 from ..array import (view_shape, coerce_numeric, stack_view, unique, broadcast_to,
                      shape_to_string, check_sorted, pretty_number, unbroadcast,
-                     iterate_chunks, combine_slices, nanmean, nanmedian, nansum, nanmin, nanmax)
+                     iterate_chunks, combine_slices, nanmean, nanmedian, nansum,
+                     nanmin, nanmax, format_minimal)
 
 
 @pytest.mark.parametrize(('before', 'ref_after', 'ref_indices'),
@@ -229,3 +230,32 @@ def test_combine_slices_hypot(beg1, end1, stp1, beg2, end2, stp2, length):
         actual = list(range(*combine_slices(slice1, slice2, length).indices(length)))
 
         assert actual == expected
+
+
+def test_format_minimal():
+
+    # TODO: in future could consider detecting integer cases
+    fmt, strings = format_minimal([133, 1444, 3300])
+    assert fmt == "{:.1f}"
+    assert strings == ['133.0', '1444.0', '3300.0']
+
+    # TODO: in future could consider detecting if all intervals are integers
+    fmt, strings = format_minimal([133., 1444., 3300.])
+    assert fmt == "{:.1f}"
+    assert strings == ['133.0', '1444.0', '3300.0']
+
+    fmt, strings = format_minimal([3, 4.3, 4.4, 5])
+    assert fmt == "{:.1f}"
+    assert strings == ['3.0', '4.3', '4.4', '5.0']
+
+    fmt, strings = format_minimal([3, 4.325, 4.326, 5])
+    assert fmt == "{:.3f}"
+    assert strings == ['3.000', '4.325', '4.326', '5.000']
+
+    fmt, strings = format_minimal([-3, 0., 0.993e-4, 5])
+    assert fmt == "{:.4f}"
+    assert strings == ['-3.0000', '0.0000', '0.0001', '5.0000']
+
+    fmt, strings = format_minimal([-3, 0., 0.993e-8, 5])
+    assert fmt == "{:.1e}"
+    assert strings == ['-3.0e+00', '0.0e+00', '9.9e-09', '5.0e+00']

glue/viewers/common/qt/data_slice_widget.py

@@ -6,7 +6,7 @@
 
 from qtpy import QtCore, QtWidgets
 from glue.utils.qt import load_ui
-from glue.utils import nonpartial
+from glue.utils import nonpartial, format_minimal
 from glue.icons.qt import get_icon
 from glue.core.state_objects import State, CallbackProperty
 from glue.external.echo.qt import autoconnect_callbacks_to_qt
@@ -72,13 +72,7 @@ def __init__(self, label='', world=None, lo=0, hi=10,
         # a string, every string value is different.
 
         if world is not None and len(world) > 1:
-            if np.max(np.abs(world)) > 1e5 or np.max(np.abs(world)) < 1e-5:
-                fmt_type = 'e'
-            else:
-                fmt_type = 'f'
-            relative = np.abs(np.diff(world) / world[:-1])
-            ndec = max(2, min(int(np.ceil(-np.log10(np.min(relative)))) + 1, 15))
-            self.label_fmt = "{:." + str(ndec) + fmt_type + "}"
+            self.label_fmt = format_minimal(world)[0]
         else:
             self.label_fmt = "{:g}"
 

glue/viewers/common/qt/tests/test_data_slice_widget.py

@@ -38,26 +38,26 @@ def test_slice_world(self):
 
         # Check switching between world and pixel coordinates
         s.state.slice_center = 0
-        assert s.state.slider_label == '1.00'
+        assert s.state.slider_label == '1.0'
         s.state.use_world = False
         assert s.state.slider_label == '0'
         s.state.slice_center = 3
         assert s.state.slider_label == '3'
         s.state.use_world = True
-        assert s.state.slider_label == '5.50'
+        assert s.state.slider_label == '5.5'
 
         # Round to nearest
         s.state.slider_label = '11'
         assert s.state.slice_center == 5
-        assert s.state.slider_label == '12.00'
+        assert s.state.slider_label == '12.0'
 
         # Make sure out of bound values work
         s.state.slider_label = '20'
         assert s.state.slice_center == 5
-        assert s.state.slider_label == '12.00'
+        assert s.state.slider_label == '12.0'
         s.state.slider_label = '-10'
         assert s.state.slice_center == 0
-        assert s.state.slider_label == '1.00'
+        assert s.state.slider_label == '1.0'
 
         # And disable world and try and set by pixel
         s.state.use_world = False