7.33.2 Greatest hits from previous weeks

7.33.2.1 How to calculate scalar curvature, Ricci tensor and Christoffel symbols in Mathematica?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=8895

I am seeking a convenient and effective way to calculate such geometric quantities. I've used packages like  TensoriaCalc , but they don't work at all time. Sometimes,... 
[symbolic] [physics] [tensors] [differential-geometry]
 

asked by Zoe Rowa https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1713 45 votes

answered by Yi-Zen Chu https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4869 21 votes

7.33.2.2 What does "Tag Integer is Protected" message mean?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=6738

(Newbie question) 
 
For every function I define I get this message: 
When I close and reopen Mathematica, and re-enter the function definition, I don't get the message anymore. What does it mean? 
[warning-messages]
 

asked by stevenvh https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1450 12 votes

answered by J. M.'s torpor https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=50 14 votes

7.33.2.3 How to create animated snowfall?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=16881

Well, the title is self-explanatory. What sorts of snowfall can we generate using Mathematica? There are two options I suggest to consider: 
 
1) Continuous GIF animations with smallest possible number ... 
[dynamic] [random] [animation] [generative-art]
 

asked by faleichik https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=219 40 votes

answered by Simon Woods https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=862 54 votes

7.33.2.4 How can I plot the direction field for a differential equation?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=8841

I'd like to plot the graph of the direction field for a differential equation, to get a feel for it.  I'm a novice, right now, when it comes to plotting in Mathematica, so I'm hoping that someone can ... 
[plotting] [differential-equations]
 

asked by Matt Groff https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1735 36 votes

answered by Peter Breitfeld https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=307 28 votes

7.33.2.5 Is it possible to export the equations from Mathematica to MATLAB?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=14035

Is it possible to export the output expressions from Mathematica computations (e.g., equations) in valid MATLAB syntax? 
[export] [matlab]
 

asked by Seyhmus Güngören https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4256 44 votes

answered by rm -rf https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5 49 votes

7.33.2.6 Mathematica vs. Python - how does Mathematica compare to Python's scientific computing suite?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=86058

Python's family of packages for scientific computing has matured rapidly. I can pretty much replicate all of Mathematica's functionalities, but with production level and open-source code using the ... 
[python] [system-performance]
 

asked by M.R. https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=403 60 votes

answered by Jens https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=245 38 votes

7.33.2.7 How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=66273

I'm trying to expedite some quantum mechanical calculations (expectation values etc.) by running them through Mathematica. When I say, for example, 
... 
[functions] [complex] [assumptions] [variable-definitions]
 

asked by Matthew Brunetti https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=22304 44 votes

answered by SquareOne https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=19960 27 votes