scipy-cookbook | Scipy Cookbook | Code Editor library

I am learning how to solve systems of differential equations in Python. I took a code from online (https://scipy-cookbook.readthedocs.io/items/CoupledSpringMassSystem.html) and tried to run it. I get the error message: "cannot import name 'hold' from 'pylab'". I am not sure what is wrong with the code. Can anyone tell me what is incorrect in the code below:

I played a bit with Mayavi and particularly with tvtk but I struggle finding examples in which glyphs are placed on the scene at different orientation than default.

Based on this example I prepared the following scene with two cyllinders, one red and one blue,

I have been using scipy.integrate.solve_ivp to solve a system of 2nd order ODEs.

Assuming the code available here (note this uses odeint, but similar approach with solve_ivp): https://scipy-cookbook.readthedocs.io/items/CoupledSpringMassSystem.html

Now, making some parameters (b1 and b2) time & solution-dependent, say: e.g.

I read this tutorial https://scipy-cookbook.readthedocs.io/items/CorrelatedRandomSamples.html on how to get a matrix C so that C*C^T = R, with R being a given covariance matrix. The code example implements two differents methods, Cholesky decomposition or using the eigenvalues. To my suprise printing the resulting C of the two different methods gives me two different matrices:

Eigenvalue method result:

Following this post I'm trying to implement a one-dimensional smoothing algorithm. When creating a flat window for a simple moving average the call is as follows:

I have a bunch of similar curves, for example 1000 sine waves with slightly varying amplitude, frequency and phases, they look like as in this plot:

In the above plot the color of each sine wave is from the standard pandas colormap; I would like to get a plot where the color is related to the "density" of the curves.

My first idea is to imitate an old oscilloscope screen (search for "persistence mode" or look at https://en.wikipedia.org/wiki/Eye_pattern for some background):

and so I set one color for all the curves:

but the plot is "flat" and the "density" information is not so good.

I would really like a plot like this one:

In the above plot the yellow colour means that a number of curves between 25 and 30 "pass" through the same point (or the same pixel). I hand-made the above plot and I am asking whether it can be done better and more directly with pandas or matplotlib.

Above figures are made with this program, it takes a while (a dozen or seconds) because the Bresenham's line algorithm is not optimized.

I am learning how to code on python and I am trying to figure out how I could find the sum of solutions from an ODE system at a specific time.

For example, this is from the SciPy Cookbook the example is called "Modelling a Zombie Apocalypse" https://scipy-cookbook.readthedocs.io/items/Zombie_Apocalypse_ODEINT.html

Here is part of the code from the website:

I'm trying to write a simple python c-extension which includes some opencv code. Here is my c++ code: