--- a/python/moving.py	Sat Nov 13 11:20:10 2010 -0500
+++ b/python/moving.py	Fri Jan 14 19:34:00 2011 -0500
@@ -52,7 +52,8 @@
 
 
 class TimeInterval(Interval):
-    '''Temporal interval'''
+    '''Temporal interval
+    may be modified directly by setting first and last'''
 
     def __init__(self, first=0, last=-1):
         Interval.__init__(self, first, last, False)
@@ -185,13 +186,16 @@
             self.iterInstantNum += 1
             return self[self.iterInstantNum-1]
 
-    def addPosition(self, p):
+    def addPositionXY(self, x, y):
         if not self.positions:
-            self.positions = [[p.x],[p.y]]
+            self.positions = [[x],[y]]
         else:
-            self.positions[0].append(p.x)
-            self.positions[1].append(p.y)
+            self.positions[0].append(x)
+            self.positions[1].append(y)
 
+    def addPosition(self, p):
+        self.addPosition(p.x, p.y)
+        
     def draw(self, options = ''):
         from matplotlib.pylab import plot
         plot(self.positions[0], self.positions[1], options)