Plotting to file with savefig

[Ingo Dahn]

I am using the following construction in a linked cell to generate a histogramm of the data array in a file.

import matplotlib.pyplot as plt

plt.hist(data,bins=classes)

plt.savefig('Histogramm.png') 

plt.close()

Problem: When the data array changes and the linked cell is re-evaluated, the diagram is not re-generated. It is re-generated if I change the file name in the code. Is there a way to enforce regeneration of the file?

[Andrey Novoseltsev]

Here is the issue with a workaround from 4 years ago: https://github.com/sagemath/sagecell/issues/386

I suppose we just should not cache user-generated files at all. The only problem I see is with jmol that downloads the scene archive for every single file inside (so if there are 100 parts to the scene, there will be 100 downloads), but that's a bug in jmol, we can add a workaround for it, and jmol will not be default soon, hopefully.

So - does anyone think that it is a bad idea to prohibit caching of user-generated files?

[Ingo Dahn]

In the case of savefig, I'd give consistency of the image with the code a higher priority than speed.  An option or command to enforce regeneration might do as well. 

[Andrey Novoseltsev]

On Friday, 16 June 2017 06:44:02 UTC-6, Ingo Dahn wrote:

Can you please give a full page example so I know exactly what has to be fixed?

[Ingo Dahn]

See https://netmath.vcrp.de/downloads/Systeme/Sage/Stichprobe.html

Evaluate first cell, generate histogram, change and evaluate first cell, regenerate histogram - histogram unchanged.

[Andrey Novoseltsev]

On Tuesday, 27 June 2017 02:23:00 UTC-6, Ingo Dahn wrote:

See https://netmath.vcrp.de/downloads/Systeme/Sage/Stichprobe.html

Evaluate first cell, generate histogram, change and evaluate first cell, regenerate histogram - histogram unchanged.

Thank you! Should be fixed by https://github.com/sagemath/sagecell/commit/86180014e1cd574ec557c4465e96b950720b3a64 once it is live. (Still waiting for Sage 8.0 to come out to rebuild public servers.)

[Andrey Novoseltsev]

While that change is live, it does not seem to work with your page. Will try to figure out what's the difference between local and public servers here...

[Andrey Novoseltsev]

On Tuesday, 27 June 2017 02:23:00 UTC-6, Ingo Dahn wrote:

See https://netmath.vcrp.de/downloads/Systeme/Sage/Stichprobe.html

Evaluate first cell, generate histogram, change and evaluate first cell, regenerate histogram - histogram unchanged.

Works for me now with https://github.com/sagemath/sagecell/commit/b98927b87ff324716427f6d40b7a3538a7d64655 deployed on public servers. They are behind CloudFlare which apparently mangles with cache related headers, but "no-cache" gets through and for user generated files should be sensible.

[Ingo Dahn]

Confirmed. Thanks!

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