6.17.2 Greatest hits from previous weeks

6.17.2.1 Can Mathematica do symbolic linear algebra?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=3242

For instance, is there some way I can say "let A and B be arbitrary real $m\times n$ and $k\times m$ matrices, Simplify[Transpose[Transpose[A].Transpose[B]]]" and Mathematica would simplify it to B.A? 
... 
[linear-algebra] [symbolic]
 

asked by Niki Estner https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=242 63 votes

answered by Chip Hurst https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4346 6 votes

6.17.2.2 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 matrix89 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5379 56 votes

answered by Martin Ender https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=2305 71 votes

6.17.2.3 How to plot an ellipse?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=20100

I'm new to Mathematica, and I'm finding it difficult to plot an ellipse. 
I tried using 
 
Plot[(x/5)^2 + (y/3)^2 == 1, {x, -5, 5}, {y, -3, 3}] 
 
 
but I'm getting some errors. Is there something wrong  ... 
[plotting]
 

asked by Sriram https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=6075 17 votes

answered by Jens https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=245 29 votes

6.17.2.4 Standard deck of 52 playing cards in curated data?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=16108

I am not sure how to find out what all is included as curated data. For example, are the individual images of each of the 52 cards in a standard deck of playing cards included? 
 
If not, is there a way  ... 
[curated-data]
 

asked by JohnD https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1629 25 votes

answered by rm -rf https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5 23 votes

6.17.2.5 Skip header lines on import

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=50718

When importing a data file what are the comment symbols for Mathematica? 
That is, given a file like this 
 
blabla 
bulbul 
 
1 2 6 54 7 ... 
.. 
 
 
what symbol do I have to put in front of header lines so  ... 
[import] [text]
 

asked by MaxJ https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=14687 20 votes

answered by george2079 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=2079 18 votes

6.17.2.6 How to graph a sphere with cartesian equations?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=24169

I'm new to Mathematica and I need to ask how to graph a sphere, cylinder, etc.. using cartesian equations. 
 
For example in sphere's case $x^2+y^2+z^2=1$ 
 
I tried to use Plot3D but it doesn't  ... 
[plotting]
 

asked by German https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=7145 7 votes

answered by Dr. belisarius https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=193 13 votes

6.17.2.7 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 notebook, or person curve into  ... 
[graphics] [image-processing] [algorithm] [wolfram-alpha-queries] [generative-art]
 

asked by Simon https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=34 83 votes

answered by Vitaliy Kaurov https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=13 45 votes