8.1.2 Greatest hits from previous weeks

8.1.2.1 Image processing: Floor plan - detecting rooms' borders (area) and room names' texts

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=19546

Here is a simple building floor plan. I would like to derive the rooms as (rectangular) components and the names of the rooms. This is very common representation of building floor plans. 
 
The problem 
 
... 
[image-processing]
 

asked by s.s.o https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=840 65 votes

answered by Niki Estner https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=242 60 votes

8.1.2.2 How do I plot a plane EM wave?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=1987

I would like to display an electromagnetic (EM) wave.  I have written code that works, but it does not "shade" the area between the graph and the axes.  Both the ... 
[graphics] [physics] [visualization]
 

asked by Rainforest Frog https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=202 22 votes

answered by J. M. can't deal with it https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=50 16 votes

8.1.2.3 What are the most common pitfalls awaiting new users?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=18393

As you may already know, Mathematica is a wonderful piece of software. 
However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from ... 
[programming] [core-language] [faq] [guidelines]
 

asked by Dr. belisarius https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=193 510 votes

answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 298 votes

8.1.2.4 Plotting a Phase Portrait

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=14160

I'm trying to plot a phase portrait for the differential equation 
$$x'' - (1 - x^2) x' + x = 0.5 \cos(1.1 t)\,.$$ 
The primes are derivatives with respect to $t$. I've reduced this second order ODE to ... 
[plotting] [differential-equations]
 

asked by covertbob https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4528 40 votes

answered by David Slater https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1746 36 votes

8.1.2.5 How do I get the inverse of a homogeneous transformation matrix?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=106257

I want to get the inverse of this homogeneous transformation matrix: 
 
 iab = { 
{1, 0, 0, 0}, 
{0, 0, -1, 0}, 
{0, 1, 0, 3}, 
{0, 0, 0, 1} 
} 
 
 
using the ... 
[matrix] [linear-algebra] [inverse] [geometric-transform] [rotation]
 

asked by andrestoga https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=37677 5 votes

answered by march https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=29734 13 votes

8.1.2.6 How to add a vertical line to a plot

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=3561

In the plot below I would like to add two vertical lines at $x = \frac{\pi}{15} \pm \frac{1}{20}$. 
How can I do that? 
 
... 
[plotting]
 

asked by sjdh https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=515 73 votes

answered by Ajasja https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=745 89 votes

8.1.2.7 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 50 votes

answered by Jens https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=245 46 votes