Hello everyone!
Im trying to put together a system, where I can plot data read from files in
real time.
I wrote some code starting from the scrolling plot examples.
The correct plot is attached as the correct_plot.png file.
I have downsampling on:
curve.setDownsampling(ds=100, method="subsample")
All other downsampleing methods caused glitching when I resized the plot window.
Inside the update() function I check if the files is ready (another process
writes to these files):
# if the next file doesnt exist, the current is still being written to
if not os.path.exists(next_file_name):
print("File is not ready yet")
return
But whenever I reach this state, the plot starts glitching again. (See
glitch.png)
I don't know what causes this. The update() function should run similarly, as
this check is at the beginning, and if the file isn't ready, I simply return
from it.
See my code attached as well.
Sidenote:
I've seen this Github issue: ScrollingPlots Plot 3 Not
Functioning · Issue #1916 · pyqtgraph/pyqtgraph ·
GitHub<https://github.com/pyqtgraph/pyqtgraph/issues/1916>
Apparently making scrolling plots shouldn't be done using
SetPos(). What should I use instead?
What am I doing wrong? If I change - or remove - the downsampling, it just gets
worse, and the glitching starts even in "normal" conditions, e.g. without
returning prematurely because the file isn't ready.
Thanks in advance,
Gergely
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import pyqtgraph as pg
from pyqtgraph.Qt import QtCore, QtGui
import numpy as np
import os
chunk_size = 1000.0 # e.g. filesize
timeout = 130 # msec
max_chunks = 10 * 1000 / timeout # every chunk is visible for 10 seconds
win = pg.GraphicsLayoutWidget(show=True)
p5 = win.addPlot(colspan=10)
p5.setLabel('bottom', 'Samples', 'S')
p5.setLabel('left', 'TIE', 'nsec')
p5.setXRange(- int(max_chunks)*int(chunk_size), 0)
p5.setYRange(-0.1, 0.1, 0)
curves = []
data5 = np.empty((int(chunk_size),2))
def update():
global p5, data5, curves
# if the next file doesnt exist, the current is still being written to
if not os.path.exists(next_file_name):
print("File is not ready yet")
return
curve = p5.plot()
curve.setDownsampling(ds=100, method="subsample")
curves.append(curve)
last = data5[-1]
data5[0] = last
while len(curves) > max_chunks:
c = curves.pop(0)
p5.removeItem(c)
"""
Moving the plot:
every time update() is called, each chunk of data is shifted by the
chunk_size
"""
curve_pos_offset = len(curves)
for c in curves:
c.setPos( - curve_pos_offset * chunk_size, 0 )
curve_pos_offset -= 1
data5 = np.empty((int(chunk_size),2))
data5[:,0] = list(range(0, int(chunk_size)))
try:
with open(FILENAME, "r") as f:
print("Reading " + FILENAME)
i = 0
for line in f:
try:
data5[i, 1] = line.split(" ")[1]
except Exception as e:
print(e)
print("Line: " + line)
i += 1
curve.setData(x=data5[:, 0], y=data5[:, 1])
except Exception as e:
print(e)
print("Exiting...")
exit()
timer = pg.QtCore.QTimer()
timer.timeout.connect(update)
timer.start(int(timeout)) # msec
if __name__ == '__main__':
pg.exec()
