11.22.2 Greatest hits from previous weeks

11.22.2.1 How to find the position of elements in a list satisfying criteria

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=180

Say I have a list  x={2,4,6,8,10}  and I want to find out the positions of the elements that are greater than 7. 
 
... 
[list-manipulation]
 

asked by PeterR https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=140 Score of 76

answered by J. M.'s missing motivation https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=50 Score of 82

11.22.2.2 How to create a new "person curve"?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=17704

Wolfram|Alpha has a whole collectionź of parametric curves that create images of famous people. To see them, enter  WolframAlpha["person curve"]  into a Mathematica ... 
[graphics] [image-processing] [algorithm] [wolfram-alpha-queries] [generative-art]
 

asked by Simon https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=34 Score of 93

answered by Vitaliy Kaurov https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=13 Score of 50

11.22.2.3 How do I draw a pair of buttocks?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=66538

I'm trying to develop a function which 3D plot would have a buttocks like shape. 
 
Several days of searching the web and a dozen my of own attempts to solve the issue have brought nothing but two ... 
[plotting] [graphics3d] [generative-art]
 

asked by Simpleton Jack https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=22399 Score of 359

answered by mikuszefski https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=7608 Score of 559

11.22.2.4 How can I plot the direction field for a differential equation?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=8841

I'd like to plot the graph of the direction field for a differential equation, to get a feel for it.  I'm a novice, right now, when it comes to plotting in Mathematica, so I'm hoping that someone can ... 
[plotting] [differential-equations]
 

asked by Matt Groff https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1735 Score of 40

answered by Peter Breitfeld https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=307 Score of 31

11.22.2.5 How to make Jacobian automatically in Mathematica

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=5790

If we have two vectors, $a$ and $b$, how can I make Jacobian matrix automatically in Mathematica? 
 
$$ a=\left( 
\begin{array}{c} 
x_1^3+2x_2^2 \\ 
3x_1^4+7x_2 
\end{array} 
\right);b=\left( 
\begin{array}{... 
[vector-calculus]
 

asked by George Mills https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1012 Score of 46

answered by Jens https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=245 Score of 61

11.22.2.6 Find eigen energies of time-independent Schrödinger equation

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=32293

I'm trying to get the eigenvalues of a one dimensional time-independent Schrödinger equation, 
 
$-\frac{h^2}{2m_0}\frac{d^2\psi}{dx^2}+U(x)~\psi=Ei~\psi$ 
 
where U(x) is some potential and Ei is the ... 
[equation-solving] [physics] [parametric-functions]
 

asked by xslittlegrass https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1364 Score of 54

answered by Jens https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=245 Score of 49

11.22.2.7 Principal submatrix and Principal minor of a matrix

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=154018

A submatrix of a matrix is obtained by deleting any collection of rows and/or columns. 
 
For example, from the following 3-by-4 matrix, we can construct a 2-by-3 submatrix by removing row 3 and column ... 
[list-manipulation] [matrix] [programming] [linear-algebra]
 

asked by Emad kareem https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=44458 Score of 10

answered by kglr https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=125 Score of 9