2.13 Thursday, September 17, 2020

2.13.1 Top new questions this week

Display hexagon grid to visualize Langton’s ant

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230017

I am looking to recreate the following image from this reference as

using Mathematica’s Polygon documentation under "Applications" as a starting point. I want to eventually use Mathematica ...

asked by C. Fuhrman https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=60593 10 votes

answered by flinty https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72682 8 votes

Position function error

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230018

I recently upgraded from Mathematica 6 to the most recent version. In my new version the Position function returns strange results that were not present in the old ...

asked by Peter https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=74626 8 votes

answered by ciao https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=11467 11 votes

Mathematica 12.1.0.0 exporting low quality images at high ImageResolution

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=229973

I recently upgraded from Mathematica 11 to Mathematica 12.1.0.0 . I understand there were some UI changes to accommodate high resolution monitors. I’m not sure if this issue is related to that. I am ...

asked by user3556814 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=74618 8 votes

answered by Piotr Wendykier https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9239 1 vote

How can I count the color pixels in each partition of the image

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230060

I have a image of 1000 x 1000 pixels of which I have made 5 x 5 partitions. After that I am looking for a way to count number of color pixels in each partition. Thanks in advance for help.

asked by Atique Khan https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=59972 7 votes

answered by flinty https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72682 4 votes

Why does Nearest not return both equally distant values?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230082

Define the following three vectors:

a = {0., 0., 0.}; 
b = {-0.5`, 0.4330127018922193`, 0.25`}; 
c = {-0.5`, 0.`, 0.`};

Note that the distance from a to c is the ...

asked by abwatson https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1709 7 votes

answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 5 votes

BarChart does not display asymmetric error bars correctly

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230145

BarChart seems to read the uncertainty in elements the other way around. The object: Around[5, {1, 10}] is evaluated as . However, when you use it in a BarChart, the uncertainties are swapped:

asked by Luis https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=24933 6 votes

Pattern-matching complex numbers as a + bi

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230013

I just started working with Mathematica and am toying with pattern matching. There may be something obvious I’m missing in this, but I can’t figure it out by myself. I want to write down a function ...

asked by ppln https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=69266 6 votes

answered by eyorble https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=52935 5 votes

2.13.2 Greatest hits from previous weeks

Plot, extract data to a file

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=19859

I need to save data that Mathematica uses inside the Plot command. The format that I would like to have is:

x1 y1 
x2 y2 
.....

asked by molkee https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5097 30 votes

answered by Mr.Wizard https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=121 47 votes

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

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=8895

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,...

asked by Zoe Rowa https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1713 38 votes

answered by Yi-Zen Chu https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4869 18 votes

How can I improve Mathematica’s resolution on a macbook retina display?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=18419

Mathematica 9.0 looks a bit fuzzy on the retina screen, how can I increase the resolution? Here another screenshot showing a direct comparison between the browser and Mathematica

asked by Tom Wellington https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=2437 44 votes

Code that generates a mandala

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=136974

My little brother asked me to print original mandalas for coloring. I would like some idea on how to create them, but without color, so he can color them.

examples

asked by zeros https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=26849 71 votes

answered by Anton Antonov https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=34008 95 votes

How to create effect like Van Gogh’s stroke brush?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=39003

I need to apply Van Gogh’s stroke brush effect to a random image Take the following image as an example:

Thank you so much if you could help!

asked by user10495 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=10495 34 votes

answered by Simon Woods https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=862 51 votes

Find eigen energies of time-independent Schrödinger equation

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=32293

I’m trying to get the eigenvalues of a one dimensional time-independent Schrödinger equation,

\(-\frac {h^2}{2m_0}\frac {d^2\psi }{dx^2}+U(x)~\psi =Ei~\psi \)

where \(U(x)\) is some potential and Ei is the ...

asked by xslittlegrass https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1364 48 votes

answered by Jens https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=245 46 votes

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 66 votes

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

2.13.3 Can you answer these questions?

Faster alternative to ImageCorrespondingPoints?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=229962

I’m trying to use ImageCorrespondingPoints to register frames in a video sequence. Computational speed is an important consideration for the application I am ...

asked by Brady Hunt https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9017 2 votes

How to make this expression?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=230052

How to code this expression in WolframAlpha. I am interested in how to code the second sum, because it contains a boolean expression: \[\sum _{i=1}^{100}{\sum _{j>n}}{x_{i}x_{j}}\]

asked by Andrey Stebenkov https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=74632 1 vote