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Matplotlib Chart Progress Bar

Purpose: to build a graph (x, y) and move the vertical line according to the wrt graph in the timer.

I started implementing this with matplotlib. It can be implemented using the matplotlib draw () function, but it consumes a processor since it redraws every time and does not allow me to interact with the chart. so I decided to use the matplotlib animation function. in the future, I would also like to suspend a moving line. Therefore I can not use matplotlib.animation.FuncAnimatin

Problem: I'm using canvas.copy_from_bbox (ax.bbox), ax.draw_artist (string), canvas.blit (ax.bbox). But I can’t save the chart in the background and move the line above it. When I try to save, it is overwritten in a rather strange way.

This is the code I created. Can anyone help me? Thanks in advance.

import sys
import matplotlib.pyplot as p
import time
fig=p.figure();
ax = fig.add_subplot(1,1,1)

y=[];x=[];y1=[0,1000];x1=[0,0]
y=numpy.random.randn(1000,1)*100
x=numpy.arange(0,1000)
line1, = ax.plot(x,y,color='black');
ax.set_ylim(0, 1000);
line, = ax.plot(x1,y1,color='r',alpha=1,animated=True); # this is the line which i wanted to move over the graph w.r.t to time. ( i can also use axvline , but i guess its the same).
canvas = ax.figure.canvas
canvas.draw()
background = canvas.copy_from_bbox(ax.bbox); #my problem is here
starttime=time.time();
mytimer=0;
mytimer_ref=0;
def update(canvas,line,ax):
    canvas.restore_region(background) #my problem is here 
    t=time.time()-starttime;
    mytimer=t+mytimer_ref;
    x1=[mytimer,mytimer];
    line.set_xdata(x1);
    ax.draw_artist(line)
    canvas.blit(ax.bbox) #my problem is here

def onclick(event):
    global starttime
    starttime=time.time();
    global mytimer_ref;
    mytimer_ref=event.xdata;
    print "starttime",starttime;


cid=line1.figure.canvas.mpl_connect('button_press_event',onclick); # when i click the mouse over a point, line goes to that point and start moving from there. 
timer=fig.canvas.new_timer(interval=100);
args=[canvas,line,ax];
timer.add_callback(update,*args); # every 100ms it calls update function
timer.start();
p.show();
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1 answer

So it seems that the “pretty weird way” you are talking about is essentially that the wrong bbox was captured by yours background = canvas.copy_from_bbox(ax.bbox). I believe this is a known issue with most backends, where adding toolbars, etc. Affects bbox position for blitting.

Essentially, if you can capture the background after the window pops up, then everything should work for you. This can be done in several ways, in your case it is easiest to replace your command canvas.draw()with plt.show(block=False), which will open the window without making it a blocking command.

, , python, , ( ):

import sys
import matplotlib.pyplot as plt
import time
import numpy


fig = plt.figure()
ax = fig.add_subplot(111)


max_height = 100
n_pts = 100
y1 = [0, max_height]
x1 = [0, 0]
y = numpy.random.randn(n_pts) * max_height
x = numpy.arange(0, n_pts)

# draw the data
line1, = ax.plot(x, y, color='black')

# fix the limits of the plot
ax.set_ylim(0, max_height)
ax.set_xlim(0, n_pts)

# draw the plot so that we can capture the background and then use blitting
plt.show(block=False)

# get the canvas object
canvas = ax.figure.canvas
background = canvas.copy_from_bbox(ax.bbox)

# add the progress line.
# XXX consider using axvline
line, = ax.plot(x1, y1, color='r', animated=True) 


starttime=time.time()
mytimer=0
mytimer_ref=0

def update(canvas, line, ax):
    # revert the canvas to the state before any progress line was drawn
    canvas.restore_region(background)

    # compute the distance that the progress line has made (based on running time) 
    t = time.time() - starttime
    mytimer = t + mytimer_ref
    x1 = [mytimer,mytimer]
    # update the progress line with its new position
    line.set_xdata(x1)
    # draw the line, and blit the axes
    ax.draw_artist(line)
    canvas.blit(ax.bbox)

def onclick(event):
    global starttime
    starttime=time.time()
    global mytimer_ref
    mytimer_ref=event.xdata
    print "starttime",starttime


cid=line1.figure.canvas.mpl_connect('button_press_event',onclick) # when i click the mouse over a point, line goes to that point and start moving from there. 
timer=fig.canvas.new_timer(interval=100)
args=[canvas,line,ax]
timer.add_callback(update,*args) # every 100ms it calls update function
timer.start()
plt.show()

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