peus-plot: optionally give x-range as 2nd argument

Change-Id: I445ef00487fc34343f5a0333643f61753a1c4948

frappy_psi/iqplot.py

@@ -70,9 +70,10 @@ def rects(intervals, y12):
 
 
 class Plot:
-    def __init__(self, maxy):
+    def __init__(self, maxy, maxx=None):
         self.lines = {}
         self.yaxis = ((-2 * maxy, maxy), (-maxy, 2 * maxy))
+        self.maxx = maxx
         self.first = True
         self.fig = None
 
@@ -124,7 +125,7 @@ class Plot:
                 self.fig, axleft = plt.subplots(figsize=(15,7))
                 self.pause = Pause(self.fig)
                 plt.title("I/Q", fontsize=14)
-                axleft.set_xlim(0, curves[0][-1])
+                axleft.set_xlim(0, self.maxx or curves[0][-1])
                 self.ax = [axleft, axleft.twinx()]
                 self.ax[0].axhline(y=0, color='#cccccc')  # show x-axis line
                 self.ax[1].axhline(y=0, color='#cccccc')