7.37.1 Top new questions this week

7.37.1.1 Difference between HashTable datastructure and Association datastructure

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=257531

Is there a difference in the runtimes between  CreateDataStructure["HashTable"]  and  <||>  in terms of inserting, ... 
[performance-tuning] [core-language] [associations] [data-structures]
 

asked by Andrew P. https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=81674 18 votes

answered by Andrew P. https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=81674 1 vote

7.37.1.2 How to make a haunting ghost?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=257544

How to make a harmless ghost (one that looks like a flying bed sheet)? 
One can always make a Ghost Curve. 
Or one can define define a clever wiggly function with a random fluctuation. 
My initial guess ... 
[graphics] [functions]
 

asked by Sumit https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=8070 11 votes

answered by Sumit https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=8070 14 votes

7.37.1.3 Undocumented behaviour of Series in Mathematica 12.3

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=257481

I have discovered a very inconvenient behaviour of SeriesData in a new version of Mathematica v12.3.0: it automatically expands brackets in the series coefficients! 
Example: 
For the input 
... 
[bugs] [front-end] [series-expansion]
 

asked by Sergei Ovchinnikov https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=69631 9 votes

answered by LouisB https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=22158 6 votes

7.37.1.4 How can I make this rectangle in GeoGraphics look like a rectangle?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=257447

I evaluated this. 
... 
[geographics] [geodesy]
 

asked by Ted Ersek https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=460 9 votes

answered by Michael Seifert https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=27813 12 votes

7.37.1.5 Why doesn't Mathematica know the exact value of some trivial trigonometric functions?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=257468

The trigonometric functions for half angles have well-defined and simple rules. For example 
$$\tan\left(\frac x2\right)=\frac{\sin x}{1+\cos x}=\frac1{\csc x+\cot x}$$ 
But I can't get the exact value ... 
[simplifying-expressions] [trigonometry]
 

asked by polfosol https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=37848 8 votes

answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 8 votes

7.37.1.6 Why is WeightedData slow?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=257723

I have been using  WeightedData  with  Histogram ,  HistogramList , ... 
[performance-tuning] [histograms]
 

asked by anonymous https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=67696 7 votes

7.37.1.7 What Does this Syntax Mean in Ouput from DSolve?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=257599

When I run the code 
 DSolve[y*D[f[x, y, z], z] - z*D[f[x, y, z], y] == 0, 
f[x, y, z], {x, y, z}] 
 
I get the following output. 
 
I don't understand this syntax. I ... 
[differential-equations] [equation-solving] [syntax] [variable] [arguments]
 

asked by Just Some Old Man https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=12697 5 votes

answered by Nasser https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=70 6 votes