搜索讨论

Emma Farnan
上次活动时间: 2023-11-28

Add alpha capability to "Line" class

I think it would be a really great feature to be able to add an Alpha property to the basic "Line" class in MATLAB plots. I know that I have previously had to resort to using Patch to be able to plot semitransparent lines, but there are also so many other functions that rely on the "Line" class.

For example, if you want to make a scatter plot from a table with things specified into groups, you can use ScatterHistogram or gscatter but since gscatter uses the Line class, you can't adjust the marker transparency. So if you don't want the histograms, you are stuck with manually separating it and using scatter with hold on.

Mishal Mohanlal
上次活动时间: 2023-11-17

Compression only spring mass system

Hi Guys

Posting this based on a thought I had, so I don't really ahve any code however I would like to know if the thought process is correct and/or relatively accurate.

Consider a simple spring mass system which only allows compression on the spring however when there is tension the mass should move without the effect of the spring distrupting it, thus the mass is just thrown vertically upwards.

The idea which I came up with for such a system is to have two sets of dfferential equations, one which represents the spring system and another which presents a mass in motion without the effects of the spring.

Please refer to the below basic outline of the code which I am proposing. I believe that this may produce relatively decent results. The code essentially checks if there is tension in the system if there is it then takes the last values from the spring mass differential equation and uses it as initial conditions for the differential equation with the mass moving wothout the effects of the spring, this process works in reverse also. The error which would exist is that the initial conditions applied to the system would include effects of the spring. Would there be a better way to code such behaviour?

function xp = statespace(t,x,f,c,k,m)
    if (k*x(1)) positive #implying tension
      **Use last time step as initial conditions**
      **differential equation of a mass moving""
    end
    if x(1) negative #implying that the mass in now moving down therefore compression in spring
      **Use last time step as initial conditions**
      **differential equation for a spring mass system**
    end
end

Martin Ryba
上次活动时间: 2023-12-12

AWGN SNR calibration for band limited signals

Seeing a colleague make this mistake (one I've had to fix multiple times in other's work too) makes me want to ask the community: would you like the awgn() function/blocks to give the option for creating a SNR at the bandwidth of the signal? Your typical flow is something like this:

Create a signal, usually at some nominal upsampling factor (e.g., 4) such that it's now nicely over sampled, especially if you're using a RRC or similar pulse shaping filter.
Potentially add a frequency offset (which might make the sample frequency even higher)
Add AWGN channel model for a desired SNR
Put this into your detector/receiver model

The problem is, when someone says, "I'm detecting XYZ at foo SNR," it should not magically improve as a function of the oversample. The problem isn't that awgn() generates white noise, that's what it's supposed to do and the typical receiver has noise across the entire band. The problem is that SNR is most properly defined as the signal power over the noise power spectral density times the signal's noise equivalent bandwidth. Now I looked and there's no handy function for computing NEBW for an input signal (there's just a function for assessing analysis windows). In practice it can get a bit tricky. The occupied bandwidth or HPBW are often close enough to the NEBW, we're usually not haggling over hundredths of a dB. So, in my not so humble opinion, the "measured" flag for awgn() should give an option for bandwidth matching or at least document the behavior better in the help page. All too often I'm seeing 3-6 (or worse) dB errors because people aren't taking the signal's bandwidth into account.

David
上次活动时间: 2023-10-31

See what's going on at MATLAB Central without leaving MATLAB 🙂

Here's a MATLAB class I wrote that leverages the MATLAB Central Interface for MATLAB toolbox, which in turn uses the publicy available Community API. Using this class, I've created a few Favorites that show me what's going on in MATLAB Central - without having to leave MATLAB 🙂

The class has a few convenient queries:

Results for the last 7 days
Results for the last 30 days
Results for the current month
Results for today

And supporting a bunch of different content scopes:

All MATLAB Central
MATLAB Answers
Blogs
Cody
Contests
File Exchange
Exclude Answers content

The results are displayed in the command window (which worked best for me) and link to each post. Here's what that looks like for this command

>> CommunityFeed.thisMonth("app designer", CommunityFeed.Scope.ExcludeAnswers)

Let me know if you find this class useful and feel free to suggest changes.

Ben Pasquariello
上次活动时间: 2023-10-25

New Cheat Sheet for Organizing and Accessing Data in MATLAB

New Cheat Sheet Alert!

Level up your data organization and access skills in MATLAB with our latest cheat sheet! Download the full cheat sheet on MATLAB GitHub for Students here.

Julian
上次活动时间: 2024-2-5

Naming x-values in bar(x,y)

I know the latest version of MATLAB R2023b has this feature already, put it should be added to R2023a as well because of its simplicity and convenience.

Basically, I want to make a bar graph that lets me name each column in a basic bar graph:

y=[100 99 100 200 200 300 500 800 1000];

x=["0-4" "5-17" "18-29" "30-39" "40-49" "50-64" "65-74" "75-84" "85+"];

bar(x,y)

However, in R2023a, this isn't a feature. I think it should be added because it helps to present data and ideas more clearly and professionally, which is the purpose of a graph to begin with.

Matt J
上次活动时间: 2024-3-1

Implicit expansion for CAT()

Would it be a good thing to have implicit expansion enabled for cat(), horzcat(), vertcat()? There are often situations where I would like to be able to do things like this:

 x=[10;20;30;40];
 y=[11;12;13;14];
 z=cat(3, 0,1,2);
 
 C=[x,y,z]
 

with the result,

Chen Lin
上次活动时间: 2023-11-3

AI + Community: How Can We Embrace Generative AI to Enhance Community Management

In the past year, we've witnessed an exponential growth of ChatGPT and other Generative AI tools. AI has quickly become a transformative force across industries, from tech giants to small startups, and even community sites like ours. For instance, Stack Overflow announced its plan to leverage AI tools to draft a question or tag content; Quora built a ChatGPT bot to answer questions; and GitHub is piloting the AI tool for personalized content.

This trend in the community landscape makes me wonder what MATLAB Central community, especially in MATLAB Answers, can do to integrate AI and enhance the community.

Share with us your ideas in the comment session. Ideally one comment per idea, so that others can vote on a secific idea or have deeper discussions about it.

Chen Lin
上次活动时间: 2023-10-11

Do you like the channels we have in Discussions area?

We launched the Discussions area with 6 channels, based on the existing types of content we see today in the MATLAB Central community.

I'm curious which channels you are most interested in participating, or which channels are missing.

Tell us your thoughts here!

channels

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

Walter Roberson
上次活动时间: 2023-10-6

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
上次活动时间: 2024-7-27

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

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

Walter Roberson
上次活动时间: 2023-12-27

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
上次活动时间: 2023-10-4

"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
上次活动时间: 2023-10-4

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.

Ben Pasquariello
上次活动时间: 2024-1-19

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

Mike Croucher
上次活动时间: 2023-10-14

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)

Rik
上次活动时间: 2024-2-7

MATLAB Answers Wish-list #6 (and bug reports)

This is the 6th installment of the wish-list and bug report thread.

This topic is the follow on to the first Wish-list for MATLAB Answer sections and second MATLAB Answers Wish-list #2 (and bug reports). The third started out as New design of the forum - grey on white and the fourth and fifth also grew so large they are slow to load and navigate.

Same idea as the previous ones: one wish (or bug report) per answer, so that people can vote their wishes.

What should you post where?

Wishlist threads (#1 #2 #3 #4 #5 #6): bugs and feature requests for Matlab Answers

Frustation threads (#1 #2): frustations about usage and capabilities of Matlab itself

Missing feature threads (#1 #2): features that you whish Matlab would have had

Next Gen threads (#1): features that would break compatibility with previous versions, but would be nice to have

@anyone posting a new thread when the last one gets too large (about 50 answers seems a reasonable limit per thread), please update this list in all last threads. (if you don't have editing privileges, just post a comment asking someone to do the edit)

John D'Errico
上次活动时间: 2022-11-10

linprog failed to work. why? Did I do something wrong?

I've now seen linear programming questions pop up on Answers recently, with some common failure modes for linprog that people seem not to understand.

One basic failure mode is an infeasible problem. What does this mean, and can it be resolved?

The most common failure mode seems to be a unbounded problem. What does this mean? How can it be avoided/solved/fixed? Is there some direction I can move where the objective obviously grows without bounds towards +/- inf?

Finally, I also see questions where someone wants the tool to produce all possible solutions.

A truly good exposition about linear programming would probably result in a complete course on the subject, and Aswers is limited in how much I can write (plus I'll only have a finite amount of energy to keep writing.) I'll try to answer each sub-question as separate answers, but if someone else would like to offer their own take, feel free to do so as an answer, since it has been many years for me since I learned linear programming.