vispy | Main repository for Vispy | Data Visualization library

I want to add an arrow (some object) upon the press of a button. The code is a modified version of the example given in the vispy repository.

I tried googling and piecing together an example from many sources. Here is what I've got:

I am currently using pyqtgraph to visualize realtime data for 64 independent data traces/plots. While the speed is realtively good, I noticed a serious slow down if the sample buffer length reaches beyond 2000 points. Profiling the following code yields that functions.py:1440(arrayToQPath) seems to have a major impact:

Going off of the examples/basics/visuals/graphy.py, I tried to display a histogram but failed:

I have seen other questions on the topic on this forum, but none have helped me understand how to deal with this. Most of them also seem to me to be about quite intricated and long code. I believe I am doing something rather simple / would like to do something rather simple. I hope someone can help! Here below extensive explanations and then my current code.

NOTE: please do not delete this question. I have given the following a lot of thought and I have carefully gone through related threads, but to no avail. I also believe it makes sense to post this because it is partly related to a more generic question: that of how to plot in real-time while having callbacks running in the background (see summary at the end), which could be summarized to be my general goal.

Setup and goal: National Instruments acquisition module (this matters litlle) NI cDAQ9178, interfaced via nidaqmx-python, a package maintained by NI with documentation here. Some analog signal is inputed in there, and the goal is to acquire it continuously (until I decide to stop the acquisition) at a certain sampling rate (approximately 1000 Hz) while plotting the signal in real time. The plotting needs not be refreshed nearly so often (10Hz refresh rate would even be fine). I'm using Windows 10 with Python 3.7 in a conda virtual environment, and editing is done in PyCharm. Ideally things should work both in PyCharm and any terminal.

Situation: nidaqmx-python provides high-level functions that allow one to register callbacks (which one defines as one wishes), which are called everytime a certain number of samples (in my case 100, but that's not strict) fills the PC buffer. The idea is that the callback, defined below, reads the buffer at that point, and does something (in my case some low-pass filtering, which I have taken out for conciseness, some storing into a global variable data, and maybe plotting - see below).

Problem: I have been fooling around with having whatever plots the data in real time be included in the callback, but with matplotlib that is a nightmare because the callback uses threads other than the main one, and matplotlib does not like to be called from anywhere outside the main thread. I've googled the heck out of other libraries optimized for real-time plotting (and, I was thinking, hopefully thread safe) but it's not so easy: I cannot get vispy to work and I cannot get pyqtgraph to even install, just to give you some examples. Then I saw several posts on the internet of people actually managing pretty decent real-time animations with matplotlib, despite it having been developped with publication in mind and not these applications; so I thought let's give it a go.

My take: Since I could not have matplotlib do the work from inside the callback, I did the following (which is the code you see below): after the callback and after the task is started with task.start() (that's specific to nidaqmx-python), I just create a while loop which plots the global variable buffer. I thought it was a nice trick: see, buffer is updated (call it that) by the callback every 0.1 seconds or so (does not matter) and, on the side, the while loop is plotting the buffer variable over and over, erasing everytime before plotting, effectively yielding a real-time like plot.

NOTE: I am perfectly aware the plotting part is not nearly as good as it could be made (I probably should use the ax API of matplotlib and the subplots, not to mention animation), but I do not care for the moment. I'll deal with that later and refine it to make it more efficient.

What I want: this actually does what I want ... except, in order to stop it, I introduced the try: and except: statements around the while loop, as you see in the code below. Naturally, pressing CTRL+C does break the loop ... but it then also breaks the whole running script and leaves me with the following error: forrtl: error (200): program aborting due to control-C event, in PyCharm, and the following precision when run from a terminal:

I'm currently evaluating vispy for my interactive plotting needs. While it feels a bit beta-ish I'm rather impressed with its speed. Also API design-wise it looks promising.

One feature I'd need to work is picking plot elements with the mouse. There is one example in the distribution (0.6.4) that promises to do precisely that: examples/demo/scene/picking.py. Unfortunately it doesn't work for me.

It displays a single window containing a graph with multiple lines. I can interact with the plot as whole, i.e. zoom and shift, but I cannot select individual lines.

If I monkey-debug the relevant piece of code (print statement is mine, full example is at github):

In vispy library I have a list of points shown as markers, and I want to change the color of(or just get the index of) the point which is nearest to the clicked point.

I can get the pixels of the clicked point by event.pos, but i need its actual co-ordinate to compare it with others (or get pixel point of other markers to compare it with the event location).

I have this code to get the nearest point index.which takes input of an array and a point(clicked one)

Due to a bug still present in Tensorflow 1.0.1 release for windows I have installed the latest nightly build tensorflow cpu

Unfortunately with this version, now kernel crashes for a different reason and I get this error:

I'd like to create a python3.6 env with default anaconda packages. The manual and many online resources say the command is conda create -n py36 python=3.6 anaconda. On other computers that works, but on one particular computer it only installs very few packages. I can't figure out why. I've checked $HOME/anaconda2/env and there's nothing in there. (ubuntu 16.04, installed from anaconda, not miniconda)