feat: extend reward plot for multiple signals (#11)

* feat: extend reward plot for multiple signals

* fix: differentiate between scalar and array reward in plot utility

src/dm_robotics/panda/utils.py

@@ -256,19 +256,35 @@ def __init__(self,
                maxlen: int = 500) -> None:
     super().__init__(runtime, maxlen)
     self.fig.title = 'Reward'
-    self.maxlines = 1
-    self.y.append(deque(maxlen=self.maxlen))
+    self.maxlines = None
+
+  def _init_buffer(self):
+    if isinstance(self._rt._time_step.reward, np.ndarray):
+      self.maxlines = self._rt._time_step.reward.shape[0]
+    else:
+      self.maxlines = 1
+    for _1 in range(self.maxlines):
+      self.y.append(deque(maxlen=self.maxlen))
     self.reset_data()
 
   def render(self, context, viewport):
-    if self._rt._time_step is None:
+    if self._rt._time_step is None or self._rt._time_step.reward is None:
       return
-    r = self._rt._time_step.reward
-    self.fig.linepnt[0] = self.maxlen
-    self.y[0].append(r)
-    self.fig.linedata[0][:self.maxlen * 2] = np.array([self.x,
-                                                       self.y[0]]).T.reshape(
-                                                           (-1,))
+    if self.maxlines is None:
+      self._init_buffer()
+    if self.maxlines > 1:
+      for i, r in enumerate(self._rt._time_step.reward):
+        self.fig.linepnt[i] = self.maxlen
+        self.y[i].append(r)
+        self.fig.linedata[i][:self.maxlen * 2] = np.array([self.x, self.y[i]
+                                                          ]).T.reshape((-1,))
+    else:
+      r = self._rt._time_step.reward
+      self.fig.linepnt[0] = self.maxlen
+      self.y[0].append(r)
+      self.fig.linedata[0][:self.maxlen * 2] = np.array([self.x,
+                                                         self.y[0]]).T.reshape(
+                                                             (-1,))
     pos = mujoco.MjrRect(2 * 300 + 5, viewport.height - 200 - 5, 300, 200)
     mujoco.mjr_figure(pos, self.fig, context.ptr)