如何在pyqtgraph中缩放绘图

Question

I don't know how to operate the plot to be zoomed.
This plot draw random function in real time.
I want to zoom the plot in real time for specified region.
This code is example code in pyqtgraph. This code works right for fixed data.
Is it impossible the plot moving in real time to zoom? Would you please help me?

# -*- coding: utf-8 -*-

import pyqtgraph as pg
from pyqtgraph.Qt import QtCore, QtGui
import numpy as np

win = pg.GraphicsWindow()
win.setWindowTitle('Scroll and Zoomed Plot')

plotScroll = win.addPlot()
plotScroll.setDownsampling(mode='peak')
plotScroll.setClipToView(True)
curveScroll = plotScroll.plot()

dataRnd = np.empty(100)
ptrDataRnd = 0

def updateScroll():
    global dataRnd, ptrDataRnd
    dataRnd[ptrDataRnd] = np.random.normal()
    ptrDataRnd += 1
    if ptrDataRnd >= dataRnd.shape[0]:
        tmp = dataRnd
        dataRnd = np.empty(dataRnd.shape[0] * 2)
        dataRnd[:tmp.shape[0]] = tmp
    curveScroll.setData(dataRnd[:ptrDataRnd])

LinRegionItem = pg.LinearRegionItem([0,100])
LinRegionItem.setZValue(-10)
plotScroll.addItem(LinRegionItem)

win.nextRow()

plotZoom = win.addPlot(title="Zoomed graph for Random plot ")
plotZoom.plot(dataRnd, pen=(255,255,255,200))

def updatePlot():
    plotZoom.setXRange(*LinRegionItem.getRegion(), padding=0)
def updateRegion():
    LinRegionItem.setRegion(plotZoom.getViewBox().viewRange()[0])
LinRegionItem.sigRegionChanged.connect(updatePlot)
plotZoom.sigXRangeChanged.connect(updateRegion)
updatePlot()

# update all plots
def update():
    updateScroll()

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_()

Answer 1

I also solved this problem. I revised the code as shown below line.

Before revision:

curveZoom.setData(dataRnd[:ptrDataRnd])  

revised code:

curveZoom.setData(dataRnd[0:ptrDataRnd])

I wonder the convention of the numpy array. The meaning of "dataRnd[:ptrDataRnd]" is to specify range from 0th to ptrDataRnd. Am I wrong? Please tell me the truth.