10.21.2 Greatest hits from previous weeks

10.21.2.1 Is there a syntax for single-line comments for notebooks?
10.21.2.2 Elegant operations on matrix rows and columns
10.21.2.3 Why I get the "Set::write: "Tag Times in is Protected." error?
10.21.2.4 Plotting a Phase Portrait
10.21.2.5 How to manipulate 2D plots?
10.21.2.6 Placing text within a plot
10.21.2.7 Is it possible to recover an unsaved notebook after closing it?
10.21.2.1 Is there a syntax for single-line comments for notebooks?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=1496

I'm aware that I can use  (* ... *)  to comment out stuff in a notebook. Many languages have a syntax for single-line comments, such as 
 
... 
[syntax] [comment]
 
asked by Peeter Joot https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=10 Score of 83
answered by Szabolcs https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=12 Score of 86
10.21.2.2 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 205
answered by Mr.Wizard https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=121 Score of 70
10.21.2.3 Why I get the "Set::write: "Tag Times in is Protected." error?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=11868

Why I get the error below with this code: 
 
... 
[vector-calculus]
 
asked by Aurelius https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1669 Score of 11
answered by Mark McClure https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=36 Score of 15
10.21.2.4 Plotting a Phase Portrait

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=14160

I'm trying to plot a phase portrait for the differential equation 
$$x'' - (1 - x^2) x' + x = 0.5 \cos(1.1 t)\,.$$ 
The primes are derivatives with respect to $t$. I've reduced this second order ODE to ... 
[plotting] [differential-equations]
 
asked by covertbob https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4528 Score of 47
answered by David Slater https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1746 Score of 42
10.21.2.5 How to manipulate 2D plots?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=7142

When it comes to visual analysis, large datasets or data with intricate internal details often makes plotting in 2D useless, as the outcome is either just a fraction of the full dataset, or no details ... 
[plotting] [graphics] [dynamic] [gui-construction]
 
asked by István Zachar https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=89 Score of 146
answered by István Zachar https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=89 Score of 166
10.21.2.6 Placing text within a plot

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=71776

I want to place text within a plot. The text is always centered relative to the coordinates. How can I left-align or right-align the text relative to the coordinates? For example: 
 
... 
[plotting] [graphics] [text]
 
asked by Anthony Mannucci https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=24733 Score of 29
10.21.2.7 Is it possible to recover an unsaved notebook after closing it?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=74205

I just Ctrl-Alt-Deleted out of Mathematica after I crashed it while running. I had not saved it all day and had done quite a lot of work on it. When I reopen the file, it shows a version with none of ... 
[crash] [save]
 
asked by Shane https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=25422 Score of 13
answered by bbgodfrey https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1063 Score of 11