5.2.2 Greatest hits from previous weeks

5.2.2.1 How to calculate scalar curvature Ricci tensor and Christoffel symbols in Mathematica?

https://mathematica.stackexchange.com/questions/8895/how-to-calculate-scalar-curvature-ricci-tensor-and-christoffel-symbols-in-mathem

 
I am seeking a convenient and effective way to calculate such geometric quantities. I've used packages like TensoriaCalc, but they don't work at all time. Sometimes, I run into the following error: 
 
 
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- asked by Zoe Rowa (29 votes), answered by Yi-Zen Chu (12 votes)

5.2.2.2 xkcd-style Plots

https://mathematica.stackexchange.com/questions/11350/xkcd-style-plots

 
 
 
I received an email to which I wanted to respond with a xkcd-style graph, but I couldn't manage it. Everything I drew looked perfect, and I don't have enough command over PlotLegends to have these  ...
                                                                                  

                                                                                  
 

- asked by Amatya (554 votes), answered by Simon Woods (409 votes)