Initial work on supporting units in the scatter viewer

glue/viewers/scatter/state.py

@@ -2,7 +2,7 @@
 
 import numpy as np
 
-from glue.core import BaseData, Subset
+from glue.core import BaseData, Subset, Data
 
 from glue.config import colormaps
 from glue.viewers.matplotlib.state import (MatplotlibDataViewerState,
@@ -14,6 +14,7 @@
 from glue.core.data_combo_helper import ComponentIDComboHelper, ComboHelper
 from glue.core.exceptions import IncompatibleAttribute
 from glue.viewers.common.stretch_state_mixin import StretchStateMixin
+from glue.core.units import find_unit_choices
 
 from matplotlib.projections import get_projection_names
 
@@ -34,6 +35,9 @@ class ScatterViewerState(MatplotlibDataViewerState):
     x_limits_percentile = DDCProperty(100, docstring="Percentile to use when automatically determining x limits")
     y_limits_percentile = DDCProperty(100, docstring="Percentile to use when automatically determining y limits")
 
+    x_display_unit = DDSCProperty(docstring='The units to use to display the x-axis.')
+    y_display_unit = DDSCProperty(docstring='The units to use to display the y-axis')
+
     def __init__(self, **kwargs):
 
         super(ScatterViewerState, self).__init__()
@@ -43,11 +47,13 @@ def __init__(self, **kwargs):
         self.x_lim_helper = StateAttributeLimitsHelper(self, attribute='x_att',
                                                        lower='x_min', upper='x_max',
                                                        log='x_log', margin=0.04,
+                                                       display_units='x_display_unit',
                                                        limits_cache=self.limits_cache)
 
         self.y_lim_helper = StateAttributeLimitsHelper(self, attribute='y_att',
                                                        lower='y_min', upper='y_max',
                                                        log='y_log', margin=0.04,
+                                                       display_units='y_display_unit',
                                                        limits_cache=self.limits_cache)
 
         self.add_callback('layers', self._layers_changed)
@@ -68,6 +74,9 @@ def __init__(self, **kwargs):
         self.add_callback('x_log', self._reset_x_limits)
         self.add_callback('y_log', self._reset_y_limits)
 
+        self.add_callback('x_att', self._update_x_display_unit_choices)
+        self.add_callback('y_att', self._update_y_display_unit_choices)
+
         if self.using_polar:
             self.full_circle()
 
@@ -197,6 +206,36 @@ def _layers_changed(self, *args):
 
         self._layers_data_cache = layers_data
 
+    def _update_x_display_unit_choices(self, *args):
+
+        # NOTE: only Data and its subclasses support specifying units
+        if self.x_att is None or not isinstance(self.x_att.parent, Data):
+            ScatterViewerState.x_display_unit.set_choices(self, [])
+            return
+
+        component = self.x_att.parent.get_component(self.x_att)
+        if component.units:
+            x_choices = find_unit_choices([(self.x_att.parent, self.x_att, component.units)])
+        else:
+            x_choices = ['']
+        ScatterViewerState.x_display_unit.set_choices(self, x_choices)
+        self.x_display_unit = component.units
+
+    def _update_y_display_unit_choices(self, *args):
+
+        # NOTE: only Data and its subclasses support specifying units
+        if self.y_att is None or not isinstance(self.y_att.parent, Data):
+            ScatterViewerState.y_display_unit.set_choices(self, [])
+            return
+
+        component = self.y_att.parent.get_component(self.y_att)
+        if component.units:
+            y_choices = find_unit_choices([(self.y_att.parent, self.y_att, component.units)])
+        else:
+            y_choices = ['']
+        ScatterViewerState.y_display_unit.set_choices(self, y_choices)
+        self.y_display_unit = component.units
+
 
 def display_func_slow(x):
     if x == 'Linear':

glue/viewers/scatter/tests/test_viewer.py

@@ -1,5 +1,5 @@
 import numpy as np
-from numpy.testing import assert_allclose
+from numpy.testing import assert_allclose, assert_equal
 
 import matplotlib.pyplot as plt
 
@@ -8,8 +8,9 @@
 from glue.viewers.scatter.viewer import SimpleScatterViewer
 from glue.core.application_base import Application
 from glue.core.data import Data
-from glue.core.link_helpers import LinkSame
+from glue.core.link_helpers import LinkSame, LinkSameWithUnits
 from glue.core.data_derived import IndexedData
+from glue.core.roi import RectangularROI
 
 
 @visual_test
@@ -131,3 +132,113 @@ def test_indexed_data():
 
     assert viewer.state.x_att is data_2d.main_components[0]
     assert viewer.state.y_att is data_2d.main_components[1]
+
+
+def test_unit_conversion():
+
+    d1 = Data(a=[1, 2, 3], b=[2, 3, 4])
+    d1.get_component('a').units = 'm'
+    d1.get_component('b').units = 's'
+
+    d2 = Data(c=[2000, 1000, 3000], d=[0.001, 0.002, 0.004])
+    d2.get_component('c').units = 'mm'
+    d2.get_component('d').units = 'ks'
+
+    # d3 is the same as d2 but we will link it differently
+    d3 = Data(e=[2000, 1000, 3000], f=[0.001, 0.002, 0.004])
+    d3.get_component('e').units = 'mm'
+    d3.get_component('f').units = 'ks'
+
+    d4 = Data(g=[2, 2, 3], h=[1, 2, 1])
+    d4.get_component('g').units = 'kg'
+    d4.get_component('h').units = 'm/s'
+
+    app = Application()
+    session = app.session
+
+    data_collection = session.data_collection
+    data_collection.append(d1)
+    data_collection.append(d2)
+    data_collection.append(d3)
+    data_collection.append(d4)
+
+    data_collection.add_link(LinkSameWithUnits(d1.id['a'], d2.id['c']))
+    data_collection.add_link(LinkSameWithUnits(d1.id['b'], d2.id['d']))
+    data_collection.add_link(LinkSame(d1.id['a'], d3.id['e']))
+    data_collection.add_link(LinkSame(d1.id['b'], d3.id['f']))
+    data_collection.add_link(LinkSame(d1.id['a'], d4.id['g']))
+    data_collection.add_link(LinkSame(d1.id['b'], d4.id['h']))
+
+    viewer = app.new_data_viewer(SimpleScatterViewer)
+    viewer.add_data(d1)
+    viewer.add_data(d2)
+    viewer.add_data(d3)
+    viewer.add_data(d4)
+
+    assert viewer.layers[0].enabled
+    assert viewer.layers[1].enabled
+    assert viewer.layers[2].enabled
+    assert viewer.layers[3].enabled
+
+    assert viewer.state.x_min == 0.92
+    assert viewer.state.x_max == 3.08
+    assert viewer.state.y_min == 1.92
+    assert viewer.state.y_max == 4.08
+
+    roi = RectangularROI(0.5, 2.5, 1.5, 4.5)
+    viewer.apply_roi(roi)
+
+    assert len(d1.subsets) == 1
+    assert_equal(d1.subsets[0].to_mask(), [1, 1, 0])
+
+    # Because of the LinkSameWithUnits, the points actually appear in the right
+    # place even before we set the display units.
+    assert len(d2.subsets) == 1
+    assert_equal(d2.subsets[0].to_mask(), [0, 1, 0])
+
+    # d3 is only linked with LinkSame not LinkSameWithUnits so currently the
+    # points are outside the visible axes
+    assert len(d3.subsets) == 1
+    assert_equal(d3.subsets[0].to_mask(), [0, 0, 0])
+
+    # As we haven't set display units yet, the values for this dataset are shown
+    # on the same scale as for d1 as if the units had never been set.
+    assert len(d4.subsets) == 1
+    assert_equal(d4.subsets[0].to_mask(), [0, 1, 0])
+
+    # Now try setting the units explicitly
+
+    viewer.state.x_display_unit = 'km'
+    viewer.state.y_display_unit = 'ms'
+
+    assert_allclose(viewer.state.x_min, 0.92e-3)
+    assert_allclose(viewer.state.x_max, 3.08e-3)
+    assert_allclose(viewer.state.y_min, 1.92e3)
+    assert_allclose(viewer.state.y_max, 4.08e3)
+
+    roi = RectangularROI(0.5e-3, 2.5e-3, 1.5e3, 4.5e3)
+    viewer.apply_roi(roi)
+
+    # Results are as above - the display units do not result in any changes to
+    # the actual content of the axes and does not deal with automatic conversion
+    # of different units between different datasets - LinkSameWithUnits should
+    # deal with that already.
+
+    assert_equal(d1.subsets[0].to_mask(), [1, 1, 0])
+    assert_equal(d2.subsets[0].to_mask(), [0, 1, 0])
+    assert_equal(d3.subsets[0].to_mask(), [0, 0, 0])
+    assert_equal(d4.subsets[0].to_mask(), [0, 1, 0])
+
+    # Change the limits to make sure they are always converted
+    viewer.state.x_min = 0.0001
+    viewer.state.x_max = 0.005
+    viewer.state.y_min = 200
+    viewer.state.y_max = 7000
+
+    viewer.state.x_display_unit = 'm'
+    viewer.state.y_display_unit = 's'
+
+    assert viewer.state.x_min == 0.1
+    assert viewer.state.x_max == 5
+    assert viewer.state.y_min == 0.2
+    assert viewer.state.y_max == 7

glue/viewers/scatter/viewer.py

@@ -8,6 +8,8 @@
 from glue.viewers.matplotlib.viewer import SimpleMatplotlibViewer
 from glue.viewers.scatter.state import ScatterViewerState
 from glue.viewers.scatter.layer_artist import ScatterLayerArtist
+from glue.core.units import UnitConverter
+
 
 __all__ = ['MatplotlibScatterMixin', 'SimpleScatterViewer']
 
@@ -152,9 +154,28 @@
         x_date = 'datetime' in self.state.x_kinds
         y_date = 'datetime' in self.state.y_kinds
 
-        if x_date or y_date:
-            roi = roi.transformed(xfunc=mpl_to_datetime64 if x_date else None,
-                                  yfunc=mpl_to_datetime64 if y_date else None)
+        converter = UnitConverter()
+
+        xfunc = None
+        if x_date:
+            xfunc = mpl_to_datetime64
+        else:
+            if self.state.x_display_unit:
+                xfunc = lambda x: converter.to_native(self.state.x_att.parent,
+                                                      self.state.x_att, x,
+                                                      self.state.x_display_unit)
+
+        yfunc = None
+        if y_date:
+            yfunc = mpl_to_datetime64
+        else:
+            if self.state.y_display_unit:
+                yfunc = lambda y: converter.to_native(self.state.y_att.parent,
+                                                      self.state.y_att, y,
+                                                      self.state.y_display_unit)
+
+        if xfunc or yfunc:
+            roi = roi.transformed(xfunc=xfunc, yfunc=yfunc)
 
         use_transform = not self.using_rectilinear()
         subset_state = roi_to_subset_state(roi,