8.29.1 Top new questions this week

8.29.1.1 When did this global rules change happen in Mathematica? Is this change documented?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=272871

In this Wolfram talk video  titled "Professor Richard J. Gaylord's Wolfram Language Fundamentals Part Two"  he shows at time 36:45 the following 
 
Where there are two definitions for ... 
[replacement] [core-language] [compatibility] [term-rewriting]
 

asked by Nasser https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=70 Score of 19

answered by Alexey Popkov https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=280 Score of 16

8.29.1.2 Using graphics primitives as buttons

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=272991

I am trying to use graphics primitives as buttons, but can't do it unless I rasterise first: 
... 
[graphics] [gui-construction] [button] [eventhandler]
 

asked by martin https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9923 Score of 9

answered by Lukas Lang https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=36508 Score of 11

8.29.1.3 Evaluating Pfaffian

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=272892

The Pfaffian of an even-dimensional anti-symmetric matrix $A$ is defined as: 
$$\mathrm{Pf}[A] = \frac{1}{2^{n}n!}\sum_{\pi\in S_{2n}}(-1)^{\pi} 
a_{i_{1}i_{2}}a_{i_{3}i_{4}}\cdots a_{i_{2n-1}i_{2n}... 
[matrix] [permutation]
 

asked by felix https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=87974 Score of 8

answered by Daniel Huber https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=46318 Score of 13

8.29.1.4 How to fill lower trianglar matrix with elements of a vector

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=272971

Given a dimension $n$ and a vector $v$ such as 
 n = 5 
v = Range[n (n + 1)/2] 
 
Is there any way to automate the construction of the following lower triangular matrix $... 
[matrix]
 

asked by Rudinberry https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=86546 Score of 7

answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 10

8.29.1.5 Weird black line appears in vector density plot

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=272936

Bug introduced in 13.0, persisting through 13.1. 
 
I am plotting a vector field  data  where the background color indicates the vector orientation. I use ... 
[plotting] [graphics] [bugs] [color] [vector]
 

asked by xiaohuamao https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=11125 Score of 7

answered by xzczd https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1871 Score of 7

8.29.1.6 Approximating surface with tangent planes

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=273020

I want to reproduce the effect in the figure below, approximating a surface with tangent planes, 
 
Now I can only use polygons to approximate inside the surface, although a bit similar but it's ... 
[plotting] [calculus-and-analysis] [graphics3d]
 

asked by matrix89 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5379 Score of 6

answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 7

8.29.1.7 Finding least n such that n^2 + 23 is divisible by large powers of 2

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=272981

Lets say that we want to find the least n such that n^2+23 is divisible by 2^100. 
We can compute this in one line using the Pari/GP language: 
... 
[number-theory]
 

asked by ZaMoC https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=46583 Score of 5

answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 7