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Adam Danz
Last activity 2023 年 10 月 13 日

Approximating π with durations

Over the weekend I came across a pi approximation using durations of years and weeks (image below, Wolfram, eq. 89), accurate to 6 digits using the average Gregorian year (365.2425 days).

Here it is in MATLAB. I divided by 1 week at the end rather than multiplying by its reciprocal because you can’t divide a numeric by a duration in MATLAB (1/week).

weeks = @(n)n*days(7);
piApprox = ((years(13)-weeks(6))/years(13) + weeks(3)) / weeks(1)
% piApprox = 3.141593493469302

Here’s a breakdown

The first argument becomes 12.885 yrs / 13 yrs or 0.99115
Add three weeks: 0.99115 + 3 weeks = 21.991 days
The reduced fraction becomes 21.991 days / 7 days

Now it looks a lot closer to the more familiar approximation for pi 22/7 but with greater precision!

https://www.youtube.com/watch?v=h376W93gQq4

Walter Roberson
Last activity 2023 年 10 月 6 日

full body keyboard using flag semaphore

This person used computer version to build a keyboard input, and used standard flag semaphore for the positions.

Flag semaphore is used mostly by sailors to be able to communicate optically over a distance; it does not need anything more than make-shift flags (but binoculars or telescopes can help.) Trained users can go faster than you might guess.

Hans Scharler
Last activity 2024 年 7 月 27 日

What's everyone doing today?

Chen, Rena, and I are at a community management event. It's great to be with others talking about relationships, trust, and co-creation.

community

Chen Lin
Last activity 2023 年 10 月 16 日

The Community Snacks!

I'm in a community conference in Boston today and see what snacks we get! The organizer said it's a coincidence, but it's definitly a good idea to have them in our MathWorks community meetings.

community

https://www.youtube.com/watch?v=UTUnVEiO-TU

Walter Roberson
Last activity 2023 年 12 月 27 日

Tricking AI vision systems

A research team found a way to trick a number of AI systems by injecting carefully placed nonsense -- for example being able able to beat DeepMind's Go game.

https://www.youtube.com/watch?v=SsGEcLwjgEg

Walter Roberson
Last activity 2023 年 10 月 4 日

"Cody" bridge rotates up to move out of the way

This video discusses the "Cody" bridge, which is a pedestrian bridge over a canal that has been designed to move up and out of the way when ships need to travel through. The mathematics of the bridge movement are discussed and diagrammed. It is unique and educational.

https://fb.watch/njjZFdCnC1/

Walter Roberson
Last activity 2023 年 10 月 4 日

touch microscope developed

Recently developed: a "microscope" based on touch and stereo vision.

Using touch removes the possibility of optical confusion -- for example, black on touch is only due to shape, not due to the possibility that the object has a black patch.

Sorry, you might need a Facebook account to watch the video.

Image Analyst
Last activity 2023 年 10 月 3 日

The new release is here!

(Sorry - it should be 2023b by now.)

Mike Croucher
Last activity 2024 年 5 月 10 日

spy easter egg

spy

Adam Danz
Last activity 2024 年 3 月 6 日

To hold or not to hold

I'm curious how the community uses the hold command when creating charts and graphics in MATLAB. In short, hold on sets up the axes to add new objects to the axes while hold off sets up the axes to reset when new objects are added.

When you use hold on do you always follow up with hold off? What's your reasoning on this decision?

Can't wait to discuss this here! I'd love to hear from newbies and experts alike!

graphics

Tips & Tricks

Ben Pasquariello
Last activity 2024 年 1 月 19 日

MATLAB GitHub for Students!

Calling all students! New to MATLAB or need helpful resources? Check out our MATLAB GitHub for Students repository! Find MATLAB examples, videos, cheat sheets, and more!

Visit the repository here: MATLAB GitHub for Students

Tips & Tricks

Mike Croucher
Last activity 2023 年 10 月 14 日

Want the smallest 10 elements of a large vector?

Imagine x is a large vector and you want the smallest 10 elements. How might you do it?

Details at Partial sorting in MATLAB » The MATLAB Blog - MATLAB & Simulink (mathworks.com)

Mike Croucher
Last activity 2023 年 10 月 3 日

Totally new solution framework for Ordinary Differential Equations (ODEs) in MATLAB

The way we've solved ODEs in MATLAB has been relatively unchanged at the user-level for decades. Indeed, I consider ode45 to be as iconic as backslash! There have been a few new solvers in recent years -- ode78 and ode89 for example -- and various things have gotten much faster but if you learned how to solve ODEs in MATLAB in 1997 then your knowledge is still applicable today.

In R2023b, there's a completely new framework for solving ODEs and I love it! You might argue that I'm contractually obliged to love it since I'm a MathWorker but I can assure you this is the real thing!

I wrote it up in a tutorial style on The MATLAB Blog https://blogs.mathworks.com/matlab/2023/10/03/the-new-solution-framework-for-ordinary-differential-equations-odes-in-matlab-r2023b/

The new interface makes a lot of things a much easier to do. Its also setting us up for a future where we'll be able to do some very cool algorithmic stuff behind the scenes.

Let me know what you think of the new functionality and what you think MathWorks should be doing next in the area of ODEs.

Rena Berman
Last activity 2023 年 10 月 11 日

PUZZLE: MATLAB-related word scramble

To solve the puzzle, first unscramble each of the words on the left. Then rearrange the letters in the yellow shaded boxes to complete the sentence on the right.

If you enjoyed this puzzle let me know with a like or in the comments below and I'll post more of them. Please don't post your answer, or any hints, and spoil it for those who come across this puzzle after you!! If you want to check your answer, you can messge me your guess through the link on my profile card (click on my name, Rena Berman, above and then on the envelope icon in the top right corner of the profile card that appears).