2.5.2 Greatest hits from previous weeks

2.5.2.1 How to find the position of elements in a list satisfying criteria

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=180

Say I have a list x={2,4,6,8,10} and I want to find out the positions of the elements that are greater than 7.

asked by PeterR https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=140 67 votes

answered by J. M.’s discontentment https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=50 63 votes

2.5.2.2 Finding Limits in several variables

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=21544

Is there a way to find a limit of a multivariable function, like

\[\lim _{(x,y)\to (0,0)} f(x,y)\]

with Mathematica?

When \(f\) is continuous, we can use

\[\lim _{(x,y)\to (0,0)} f(x,y)=\lim _{(x,0)}\]

asked by Dominic Michaelis https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5899 31 votes

answered by whuber https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=91 42 votes

2.5.2.3 Why round to even integers?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=2116

According to the Mathematica help:

Round rounds numbers of the form x.5 toward the nearest even integer.

For example:

Round[{0.5, 1.5, 2.5, 3.5, 4.5}]

gives

asked by wxffles https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=427 82 votes

answered by Per Alexandersson https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=488 50 votes

2.5.2.4 Why is raytracing so slow?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=219629

I’m trying to get some rays to bounce in a circle. But I want to be able to control the reflections, i.e. the direction the rays bounce in the circle. I have a MWE below, and it is severely limited by ...

asked by Tomi https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=36939 31 votes

answered by Tim Laska https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=61809 42 votes

2.5.2.5 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....

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

2.5.2.6 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, ...

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

2.5.2.7 How to make a Spherical Cow?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=125043

Being a theoretical physicist, I always have a great respect for Spherical Cow. So I thought about making one myself. I am not sure how can I create (something considered to be the simplest!) this ...

asked by Sumit https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=8070 69 votes

answered by andre314 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5467 76 votes