FreeViz: Allow setting ratio btw attractive and repulsive forces

Orange/projection/freeviz.py

@@ -21,7 +21,7 @@ class FreeViz(LinearProjector):
     projection = FreeVizModel
 
     def __init__(self, weights=None, center=True, scale=True, dim=2, p=1,
-                 initial=None, maxiter=500, alpha=0.1,
+                 initial=None, maxiter=500, alpha=0.1, gravity=None,
                  atol=1e-5, preprocessors=None):
         super().__init__(preprocessors=preprocessors)
         self.weights = weights
@@ -33,6 +33,7 @@ def __init__(self, weights=None, center=True, scale=True, dim=2, p=1,
         self.maxiter = maxiter
         self.alpha = alpha
         self.atol = atol
+        self.gravity = gravity
         self.is_class_discrete = False
         self.components_ = None
 
@@ -50,6 +51,7 @@ def get_components(self, X, Y):
             X, Y, weights=self.weights, center=self.center, scale=self.scale,
             dim=self.dim, p=self.p, initial=self.initial,
             maxiter=self.maxiter, alpha=self.alpha, atol=self.atol,
+            gravity=self.gravity,
             is_class_discrete=self.is_class_discrete)[1].T
 
     @classmethod
@@ -104,7 +106,7 @@ def forces_regression(cls, distances, y, p=1):
         return F
 
     @classmethod
-    def forces_classification(cls, distances, y, p=1):
+    def forces_classification(cls, distances, y, p=1, gravity=None):
         diffclass = scipy.spatial.distance.pdist(y.reshape(-1, 1), "hamming") != 0
         # handle attractive force
         if p == 1:
@@ -120,6 +122,8 @@ def forces_classification(cls, distances, y, p=1):
             F[mask] = 1 / distances[mask]
         else:
             F[mask] = 1 / (distances[mask] ** p)
+        if gravity is not None:
+            F[mask] *= -np.sum(F[~mask]) / np.sum(F[mask]) / gravity
         return F
 
     @classmethod
@@ -180,7 +184,8 @@ def gradient(cls, X, embeddings, forces, embedding_dist=None, weights=None):
         return G
 
     @classmethod
-    def freeviz_gradient(cls, X, y, embedding, p=1, weights=None, is_class_discrete=False):
+    def freeviz_gradient(cls, X, y, embedding, p=1, weights=None,
+                         gravity=None, is_class_discrete=False):
         """
         Return the gradient for the FreeViz [1]_ projection.
 
@@ -214,7 +219,7 @@ def freeviz_gradient(cls, X, y, embedding, p=1, weights=None, is_class_discrete=
         assert X.ndim == 2 and X.shape[0] == y.shape[0] == embedding.shape[0]
         D = scipy.spatial.distance.pdist(embedding)
         if is_class_discrete:
-            forces = cls.forces_classification(D, y, p=p)
+            forces = cls.forces_classification(D, y, p=p, gravity=gravity)
         else:
             forces = cls.forces_regression(D, y, p=p)
         G = cls.gradient(X, embedding, forces, embedding_dist=D, weights=weights)
@@ -234,7 +239,8 @@ def _rotate(cls, A):
 
     @classmethod
     def freeviz(cls, X, y, weights=None, center=True, scale=True, dim=2, p=1,
-                initial=None, maxiter=500, alpha=0.1, atol=1e-5, is_class_discrete=False):
+                initial=None, maxiter=500, alpha=0.1, atol=1e-5, gravity=None,
+                is_class_discrete=False):
         """
         FreeViz
 
@@ -341,6 +347,7 @@ def freeviz(cls, X, y, weights=None, center=True, scale=True, dim=2, p=1,
         step_i = 0
         while step_i < maxiter:
             G = cls.freeviz_gradient(X, y, embeddings, p=p, weights=weights,
+                                     gravity=gravity,
                                      is_class_discrete=is_class_discrete)
 
             # Scale the changes (the largest anchor move is alpha * radius)

Orange/widgets/visualize/owfreeviz.py

@@ -5,7 +5,7 @@
 import numpy as np
 
 from AnyQt.QtCore import Qt, QRectF, QLineF, QPoint
-from AnyQt.QtGui import QPalette
+from AnyQt.QtGui import QPalette, QFontMetrics
 from AnyQt.QtWidgets import QSizePolicy
 
 import pyqtgraph as pg
@@ -137,9 +137,13 @@ class OWFreeViz(OWAnchorProjectionWidget, ConcurrentWidgetMixin):
 
     settings_version = 3
     initialization = settings.Setting(InitType.Circular)
+    balance = False
+    gravity_index = 4
     GRAPH_CLASS = OWFreeVizGraph
     graph = settings.SettingProvider(OWFreeVizGraph)
 
+    GravityValues = [0.1, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 2.5, 3, 4, 5]
+
     class Error(OWAnchorProjectionWidget.Error):
         no_class_var = widget.Msg("Data must have a target variable.")
         multiple_class_vars = widget.Msg(
@@ -159,6 +163,7 @@ class Warning(OWAnchorProjectionWidget.Warning):
     def __init__(self):
         OWAnchorProjectionWidget.__init__(self)
         ConcurrentWidgetMixin.__init__(self)
+        self.__optimized = False
 
     def _add_controls(self):
         self.__add_controls_start_box()
@@ -177,6 +182,20 @@ def __add_controls_start_box(self):
             callback=self.__init_combo_changed,
             sizePolicy=(QSizePolicy.MinimumExpanding, QSizePolicy.Fixed)
         )
+        box2 = gui.hBox(box)
+        gui.checkBox(
+            box2, self, "balance", "Gravity",
+            callback=self.__gravity_changed)
+        self.grav_slider = gui.hSlider(
+            box2, self, "gravity_index",
+            minValue=0, maxValue=len(self.GravityValues) - 1,
+            callback=self.__gravity_dragged, createLabel=False)
+        self.gravity_label = gui.widgetLabel(box2)
+        self.gravity_label.setFixedWidth(
+            max(QFontMetrics(self.font()).horizontalAdvance(str(x))
+                for x in self.GravityValues))
+        self.gravity_label.setAlignment(Qt.AlignRight)
+        self.__update_gravity_label()
         self.run_button = gui.button(box, self, "Start", self._toggle_run)
 
     @property
@@ -189,6 +208,21 @@ def effective_data(self):
         return self.data.transform(Domain(self.effective_variables,
                                           self.data.domain.class_vars))
 
+    def __gravity_dragged(self):
+        self.balance = True
+        self.__update_gravity_label()
+        self.__gravity_changed()
+
+    def __update_gravity_label(self):
+        self.gravity_label.setText(str(self.GravityValues[self.gravity_index]))
+
+    def __gravity_changed(self):
+        gravity = self.GravityValues[self.gravity_index]
+        self.projector.gravity = gravity if self.balance else None
+        self.__update_gravity_label()
+        if self.task is None and self.__optimized:
+            self._run()
+
     def __radius_slider_changed(self):
         self.graph.update_radius()
 
@@ -232,6 +266,7 @@ def on_done(self, result: Result):
         self.projection = result.projection
         self.graph.set_sample_size(None)
         self.run_button.setText("Start")
+        self.__optimized = True
         self.commit.deferred()
 
     def on_exception(self, ex: Exception):
@@ -254,13 +289,15 @@ def init_projection(self):
             if self.initialization == InitType.Circular \
             else FreeViz.init_random(len(self.effective_variables), 2)
         self.projector = FreeViz(scale=False, center=False,
-                                 initial=anchors, maxiter=10)
+                                 initial=anchors, maxiter=10,
+                                 gravity=self.gravity if self.balance else None)
         data = self.projector.preprocess(self.effective_data)
         self.projector.domain = data.domain
         self.projector.components_ = anchors.T
         self.projection = FreeVizModel(self.projector, self.projector.domain, 2)
         self.projection.pre_domain = data.domain
         self.projection.name = self.projector.name
+        self.__optimized = False
 
     def check_data(self):
         def error(err):