text: # -*- coding: utf-8 -*-
  """
  Various methods of drawing scrolling plots.
  """
  
  import pyqtgraph as pg
  from pyqtgraph.Qt import QtCore, QtGui
  import numpy as np
  
  win = pg.GraphicsLayoutWidget(show=True)
  win.setWindowTitle('pyqtgraph example: Scrolling Plots')
  
  
  # 1) Simplest approach -- update data in the array such that plot appears to scroll
  #    In these examples, the array size is fixed.
  p1 = win.addPlot()
  p2 = win.addPlot()
  data1 = np.random.normal(size=300)
  curve1 = p1.plot(data1)
  curve2 = p2.plot(data1)
  ptr1 = 0
  def update1():
      global data1, ptr1
      data1[:-1] = data1[1:]  # shift data in the array one sample left
                              # (see also: np.roll)
      data1[-1] = np.random.normal()
      curve1.setData(data1)
      
      ptr1 += 1
      curve2.setData(data1)
      curve2.setPos(ptr1, 0)
      
  
  # 2) Allow data to accumulate. In these examples, the array doubles in length
  #    whenever it is full. 
  win.nextRow()
  p3 = win.addPlot()
  p4 = win.addPlot()
  # Use automatic downsampling and clipping to reduce the drawing load
  p3.setDownsampling(mode='peak')
  p4.setDownsampling(mode='peak')
  p3.setClipToView(True)
  p4.setClipToView(True)
  p3.setRange(xRange=[-100, 0])
  p3.setLimits(xMax=0)
  curve3 = p3.plot()
  curve4 = p4.plot()
  
  data3 = np.empty(100)
  ptr3 = 0
  
  def update2():
      global data3, ptr3
      data3[ptr3] = np.random.normal()
      ptr3 += 1
      if ptr3 >= data3.shape[0]:
          tmp = data3
          data3 = np.empty(data3.shape[0] * 2)
          data3[:tmp.shape[0]] = tmp
      curve3.setData(data3[:ptr3])
      curve3.setPos(-ptr3, 0)
      curve4.setData(data3[:ptr3])
  
  
  # 3) Plot in chunks, adding one new plot curve for every 100 samples
  chunkSize = 100
  # Remove chunks after we have 10
  maxChunks = 10
  startTime = pg.ptime.time()
  win.nextRow()
  p5 = win.addPlot(colspan=2)
  p5.setLabel('bottom', 'Time', 's')
  p5.setXRange(-10, 0)
  curves = []
  data5 = np.empty((chunkSize+1,2))
  ptr5 = 0
  
  def update3():
      global p5, data5, ptr5, curves
      now = pg.ptime.time()
      for c in curves:
          c.setPos(-(now-startTime), 0)
      
      i = ptr5 % chunkSize
      if i == 0:
          curve = p5.plot()
          curves.append(curve)
          last = data5[-1]
          data5 = np.empty((chunkSize+1,2))        
          data5[0] = last
          while len(curves) > maxChunks:
              c = curves.pop(0)
              p5.removeItem(c)
      else:
          curve = curves[-1]
      data5[i+1,0] = now - startTime
      data5[i+1,1] = np.random.normal()
      curve.setData(x=data5[:i+2, 0], y=data5[:i+2, 1])
      ptr5 += 1
  
  
  # update all plots
  def update():
      update1()
      update2()
      update3()
  timer = pg.QtCore.QTimer()
  timer.timeout.connect(update)
  timer.start(50)
  
  
  
  ## Start Qt event loop unless running in interactive mode or using pyside.
  if __name__ == '__main__':
      import sys
      if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
          QtGui.QApplication.instance().exec_()
  