9.38.1 Top new questions this week

9.38.1.1 How can I draw projection?
9.38.1.2 Is there a faster way to compose a large number of random Gaussians?
9.38.1.3 Present a logarithm in terms of two logarithms
9.38.1.4 How to Replace 'delta t' with 'a' in Mathematica Without Affecting Separate Instances of 'delta' or 't'?
9.38.1.5 Why does this pattern not match?
9.38.1.6 How to use Compile to optimize the performance of a function calculating the distance between two points?
9.38.1.7 How to accomodate empty data set in ListPlot, ListLinePlot?
9.38.1.1 How can I draw projection?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=292481

I am trying to draw this figure. 
 
I tried 
 Graphics3D[{Polygon[{{-3, -3, -2}, {-3, 3, -2}, {3, 
3, -2}, {3, -3, -2}}]}, Boxed -> False] 
 
[projection]
 
asked by Thuy Nguyen https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=69240 Score of 7
answered by cvgmt https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72111 Score of 10
9.38.1.2 Is there a faster way to compose a large number of random Gaussians?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=292273

I'm looking for a more efficient way to generate an image with a large number of randomly coloured Gaussians. Here's the code I'm using: 
... 
[performance-tuning] [image] [compile]
 
asked by flinty https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72682 Score of 6
answered by Silvia https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=17 Score of 5
9.38.1.3 Present a logarithm in terms of two logarithms

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=292531

If $\log _8 3=p$  and  $\log _3 5=q$ then, in terms of  $p$  and  $q$, what does $\log _{10} 5$  equal?  I tried by my hand, I get the answer is $\dfrac{3pq}{1+3pq}$.  How can I tell Mathematica solve ... 
[algebraic-manipulation] [algebra]
 
asked by Laurenso https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=87428 Score of 5
answered by xzczd https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1871 Score of 8
9.38.1.4 How to Replace 'delta t' with 'a' in Mathematica Without Affecting Separate Instances of 'delta' or 't'?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=292466

In Mathematica, how can I replace instances of  delta t  in an expression with  a , while keeping instances of ... 
[replacement] [pattern-matching] [algebraic-manipulation] [semantic-matching]
 
asked by Tokubara https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=87722 Score of 5
answered by Bob Hanlon https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9362 Score of 5
9.38.1.5 Why does this pattern not match?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=292331

Why does the following match? 
 MatchQ[HoldPattern[f], HoldPattern[_]] 
 
True 
 
But the following does not: 
... 
[pattern-matching]
 
asked by Daniel Huber https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=46318 Score of 5
answered by Domen https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=75628 Score of 9
9.38.1.6 How to use Compile to optimize the performance of a function calculating the distance between two points?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=292238

I want to create a function that finds the real space distance between two three-dimensional points. Each point is a list of three real numbers. 
I can create functions ... 
[performance-tuning] [compile]
 
asked by Andrew https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1185 Score of 5
answered by Karl https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=92545 Score of 7
9.38.1.7 How to accomodate empty data set in ListPlot, ListLinePlot?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=292264

The simple case often arises where multiple data sets are generated, and one or more is empty.  ListPlot  and related functions fail to plot such multidata sets. The ... 
[plotting] [data] [missing]
 
asked by István Zachar https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=89 Score of 5
answered by eldo https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=14254 Score of 4