6.11.1 Top new questions this week

6.11.1.1 Version 12.1.1 unable to type ">"

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=224461

Bug introduced in 12.1.1 
 
Since I upgraded to version 12.1.1 I am unable to use > (Shift+.). When I type Shift+. the cell that I am typing in converts to Python. What am I doing wrong? 
 
Steps to  ... 
[bugs] [front-end]
 

asked by wdacda https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=27856 15 votes

answered by Mr.Wizard https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=121 10 votes

6.11.1.2 Is there any better way to create  a, a, a, b, b, b, b, b, c, c  from   a, 3 ,  b, 5 ,  c, 2  ?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=224581

My attempt: 
data = {{a, 3}, {b, 5}, {c, 2}}; 
 
output = Table[#[[1]], #[[2]]] & /@ data // Flatten 
 
 
{a, a, a, b, b, b, b, b, c, c} 
 
 
[list-manipulation]
 

asked by Too Fat Man No Neck https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=42141 11 votes

answered by kglr https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=125 18 votes

6.11.1.3 Selecting lists where all are prime

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=224500

Given 
t={{7, 13, 19}, {13, 25, 37}, {19, 37, 55}, {25, 49, 73}, {31, 61, 91}, {37, 73, 109}} 
 
I want to select those lists where all three numbers are primes, so I should get 
{{7, 13, 19}, {37,  ... 
[list-manipulation]
 

asked by user57467 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=57467 9 votes

answered by Pillsy https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=531 12 votes

6.11.1.4 Inverting replace direction

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=224314

I just have a simple problem. I have a list such that, 
rep = { a1 -> b1, a2 -> b2, a3 -> b3}; 
 
I want to invert replace direction such that, 
{ b1 -> a1, b2 -> a2, b3 -> a3} 
 
 
[list-manipulation] [replacement]
 

asked by Saesun Kim https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=29998 8 votes

answered by PaulCommentary https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=54458 8 votes

6.11.1.5 Calculate Radius of Curvature

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=224269

I have a list of coordinates that make a near-parabolic graph, which I managed to fit and calculate the curvature. However, the curvature only outputs a equation. Is there any way to calculate the  ... 
[list-manipulation] [fitting] [parametric-functions]
 

asked by Char https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=66040 8 votes

answered by yarchik https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9469 11 votes

6.11.1.6 Legendre expansion of the Dirac delta function

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=224276

There is a known expansion for the Dirac delta function in the interval $ (-1, 1) $ in terms of the Legendre polynomials as 
$$ 
\delta(x) = \sum_{k = 0}^{\infty} (-1)^k \frac{(4k + 1) (2k)!}{2^{2k + 1}  ... 
[summation] [series-expansion] [generalized-function]
 

asked by Novice https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72595 7 votes

answered by yarchik https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9469 11 votes

6.11.1.7 Which methods are available for NDEigensystem?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=224511

I am trying to find out what methods/options are available for NDEigensystem and descriptions of their use. Perusing the help, online Q&As, Mathematica's in-line autofill, etc., I've found a few,  ... 
[differential-equations] [finite-element-method] [implementation-details] [eigenvalues]
 

asked by Eli Lansey https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9 6 votes

answered by user21 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=18437 5 votes