7.4.2 Greatest hits from previous weeks

7.4.2.1 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 29 votes

answered by Mr.Wizard https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=121 35 votes

7.4.2.2 Labeling individual curves in Mathematica

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=4444

I need to create a plot for export and inclusion in a report. Is there a better way to label curves than  PlotLegends ? From what I've read and my personal experience,... 
[plotting] [legending]
 

asked by Tianxiang Xiong https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1041 63 votes

answered by Artes https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=184 47 votes

7.4.2.3 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 61 votes

answered by Ajasja https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=745 82 votes

7.4.2.4 Drawing a square root spiral

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=66969

Here is a start. I'm looking for a nice way to draw it. 
 
... 
[graphics] [geometry]
 

asked by matrix89 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5379 24 votes

answered by Bob Hanlon https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9362 21 votes

7.4.2.5 Multivariable Taylor expansion does not work as expected

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=15023

The basic multivariable Taylor expansion formula around a point is as follows: 
 
$$ 
f(\mathbf r + \mathbf a) = f(\mathbf r) + (\mathbf a \cdot \nabla )f(\mathbf r) + \frac{1}{2!}(\mathbf a \cdot \nabla)... 
[calculus-and-analysis] [series-expansion]
 

asked by matheorem https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4742 63 votes

answered by Jens https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=245 71 votes

7.4.2.6 Solving $L=\frac 3  2  \sqrt 4 \pi ^2 A^2+W^2 -\frac \sqrt 5 W \sqrt 4 \pi ^2 A^2+W^2 +6 \pi ^2 A^2+3 W^2   \sqrt 2  +\frac 3 W  2 $ for $W$

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=57763

When I solve the aforementioned equation for $W$ or $A$ on Mathematica I get a long and ugly equation in return, namely one of the solutions for $W$ is: (attempt to read at your own health) 
 
... 
[equation-solving] [functions] [approximation]
 

asked by J.D'Almbert https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=19257 8 votes

answered by Alexei Boulbitch https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=788 15 votes

7.4.2.7 Mathematica command that allows it to read my intentions

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=194384

In version 2.0 of Mathematica there was a command,  ReadProgrammerIntentions[ ]  which allowed it rapidly compose code that could solve problems simple to complex, ... 
[machine-learning] [date-and-time] [neural-networks]
 

asked by MikeY https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=47314 52 votes

answered by MarcoB https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=27951 38 votes