9.24.2 Greatest hits from previous weeks

9.24.2.1 How to make the digits of  go around in a spiral like this?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=109982

Here is a start. 
 
 MapIndexed[Text[Reverse[First[RealDigits[Pi,10,252]]][[Tr@#2]],#]&, 
Table[{t Cos[t],t Sin[t]},{t,0,16Pi,0.2}]]//Graphics 
 
[graphics] [formatting] [generative-art]
 

asked by matrix42 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5379 Score of 59

answered by Martin Ender https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=2305 Score of 75

9.24.2.2 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 Score of 23

answered by J. M.'s lack of A.I. https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=50 Score of 17

9.24.2.3 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 Score of 80

answered by Ajasja https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=745 Score of 98

9.24.2.4 How do I identify the source of a "Tag times protected" error?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=11982

I have some code that looks like 
 
 Table[ 
a = 1; 
b = {2, 3} 
c = i;, 
{i, 2} 
] 
 
 
which gives an error: 
Set::write: Tag Times in c {2,3} is Protected.... 
[warning-messages] [syntax] [debugging] [faq]
 

asked by dearN https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=204 Score of 31

answered by Mr.Wizard https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=121 Score of 37

9.24.2.5 Plotting the frequency spectrum of a data series using Fourier

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=18082

 testData = Table[N@Sin[500 x], {x, 0, 100}]; 
ListLinePlot[Abs[Fourier[testData]], PlotRange -> Full] 
 
 
Gives me 
Which I do not expect because the Fourier ... 
[fourier-analysis]
 

asked by C. E. https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=731 Score of 14

answered by KennyColnago https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=3246 Score of 16

9.24.2.6 What does # mean in Mathematica?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=19035

I asked Mathematica to compute the following 
 
 Solve[c (1-x)^2-x^(1/4) == 0, x] 
 
 
and it returned this: 
x = Root[#1^8 c^4 - 8 #1^7 c^4 + 28 #1^6 c^4 - 56 #1^5 c^4 ... 
[syntax] [core-language]
 

asked by ronanymous https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5730 Score of 48

answered by Dr. belisarius https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=193 Score of 77

9.24.2.7 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 90

answered by Vitaliy Kaurov https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=13 Score of 48