11.18.2 Greatest hits from previous weeks

11.18.2.1 How to make a spiroglyphic?
11.18.2.2 Mathematica vs. Python - how does Mathematica compare to Python's scientific computing suite?
11.18.2.3 How can I plot the direction field for a differential equation?
11.18.2.4 How do I plot a plane EM wave?
11.18.2.5 Finding Limits in several variables
11.18.2.6 Elegant operations on matrix rows and columns
11.18.2.7 How can I create an empty JSON object?
11.18.2.1 How to make a spiroglyphic?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=188139

Some (older) members of this group might remember playing vinyl LP records. Recently, at the Abbey Road studio there was a spiroglyphics coloring book for sale. It looks like a nice programming ... 
[image-processing] [code-request] [generative-art]
 
asked by TheDoctor https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=2263 Score of 15
answered by b3m2a1 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=38205 Score of 20
11.18.2.2 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 Score of 65
answered by Jens https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=245 Score of 42
11.18.2.3 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 Score of 40
answered by Peter Breitfeld https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=307 Score of 31
11.18.2.4 How do I plot a plane EM wave?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=1987

I would like to display an electromagnetic (EM) wave.  I have written code that works, but it does not "shade" the area between the graph and the axes.  Both the ... 
[graphics] [physics] [visualization]
 
asked by Rainforest Frog https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=202 Score of 25
answered by J. M.'s missing motivation https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=50 Score of 18
11.18.2.5 Finding Limits in several variables

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=21544

Is there a way to find a limit of a multivariable function, like 
 
$$\lim_{(x,y)\to (0,0)} f(x,y)$$ 
with Mathematica? 
 
When $f$ is continuous, we can use 
$$\lim_{(x,y)\to (0,0)} f(x,y)=\lim_{(x,0)\... 
[functions] [calculus-and-analysis]
 
asked by Dominic Michaelis https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5899 Score of 35
answered by whuber https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=91 Score of 44
11.18.2.6 Elegant operations on matrix rows and columns

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=3069

Question 
 
The Mathematica tutorial has a section 'Basic Matrix Operations', describing operations like transpose, inverse and determinant. These operations all work on entire matrices. I am missing a ... 
[matrix] [list-manipulation] [faq]
 
asked by sjdh https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=515 Score of 208
answered by Mr.Wizard https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=121 Score of 70
11.18.2.7 How can I create an empty JSON object?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=50727

For creating non-empty object, I use following syntax 
 
 ExportString[{"key" -> "value"}, "JSON"] 
(*{"key" : "value"}*) 
 
 
But how can I create an empty object? ... 
[export] [conversion] [json-format]
 
asked by molekyla777 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=11981 Score of 10