Styjun

I have a mobile application which does some calculation and throws x,y coordinates and are updated on firebase every 2 seconds.

Next i want those coordinates to be plotted on a floor plan live. For that i am using Scatter plot over the floor plan image. But i cannot make it live as soon as the data is fetched need help with that.

Here is the code till now:

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.animation as animation

xs = []
ys = []
fig = plt.figure()
scat = plt.scatter(xs, ys, c='r', s=100)


def main():
 graph_data = open("testfile.txt","r").read()
 lines = graph_data.split("n")


 for line in lines:
 if len(line)>1:
 x,y = line.split(",")
 xs.append(x)
 ys.append(y)

 plt.scatter(xs,ys)
 print(xs)
 print(ys)


ani = animation.FuncAnimation(fig,main(),fargs=(scat))
plt.show()

Getting error with animation.FuncAnimation TypeError: NoneType object argument after * must be an iterable, not PathCollection

You can fetch data in a separate thread while updating the plot in the main one. Here is a complete working example:

#!/usr/bin/env python3
import time

from queue import Queue
from threading import Thread, Event

import numpy as np
import matplotlib.pyplot as plt


FETCH_DELAY = 2


def fetch_data(queue, stop):

 while not stop.is_set():
 x, y = np.random.randn(2)
 queue.put((x, y))
 time.sleep(FETCH_DELAY)


def limits(array, offset=1):
 return array.min() - offset, array.max() + offset


def main():
 stop = Event()
 queue = Queue()

 worker = Thread(target=fetch_data, args=(queue, stop))
 worker.start()

 plt.ion()
 fig, ax = plt.subplots()
 plot = ax.scatter([], [])

 try:

 while True:
 data = queue.get()

 data = np.array(data)
 plt_data = plot.get_offsets()
 plt_data = np.vstack((plt_data, data))
 plot.set_offsets(plt_data)
 fig.canvas.draw()

 xmin, xmax = limits(plt_data[:, 0])
 ymin, ymax = limits(plt_data[:, 1])

 ax.set_xlim(xmin, xmax)
 ax.set_ylim(ymin, ymax)

 queue.task_done()

 except KeyboardInterrupt:
 pass
 finally:
 stop.set()
 worker.join()


if __name__ == '__main__':
 main()

Save it as plot_update.py file and run it from the command line:

python3 plot_update.py

Here is the solution without using threads it becomes very simple:

import matplotlib.pyplot as plt
import matplotlib.animation
import numpy as np
from firebase import firebase

firebase = firebase.FirebaseApplication('Firebase url', None)

fig, ax = plt.subplots()
x, y = [],[]
sc = ax.scatter(x,y,c=np.random.rand(3,))
plt.xlim(12,13)
plt.ylim(77,78)

def animate(i):
 xs = firebase.get('/Lat',None)
 ys = firebase.get('/Long',None)
 xs = round(xs,2)
 ys = round(ys,2)
 file = open("testfile.txt","a+")
 file.write("0,1 n".format(xs,ys))
 file.close()
 graph_data = open("testfile.txt","r").read()
 lines = graph_data.split("n")
 for line in lines:
 if len(line)>1:
 xs,ys = line.split(",")
 x.append(xs)
 y.append(ys)
 sc.set_offsets(np.c_[x,y])

ani = matplotlib.animation.FuncAnimation(fig, animate, 
 frames=2, interval=500, repeat=True) 
plt.show()