Matt J
Last activity about 8 hours ago

Do Reinvent the Wheel

Are there Matlab features which intend to satisfy your needs but fail in certain critical areas, forcing you to abandon them completely in favor of your own version or a 3rd party alternative? Perhaps these features are starting to improve with new Matlab releases, but not quickly enough? Share your own frustrations in the comments below.

Here are two of mine:

1. volumeViewier

volumeViewer is 6 years old now. It is fine when you only need to view one 3D image at a time, but I never do. In my work, I am putting several images side-by-side for visual comparison. For such work, you need to be able to programmatically change axis limits and grayscale and use @doc:linkprops to reflect these changes across all the images. With 2D image comparison, all that is possible, but volumeViewer supports none of those things. So, I resort to my own 3D viewer

2.Tomographic projection commands RADON and FANBEAM

These commands are provided in the Image Processing Toolbox seemingly for no other reason than to support homework exercises for people taking introductory tomographic imaging courses. They fail in a number of ways for people who need to do serious tomographic imaging work, producing artifacts or nonlinear effects which shouldn't be there. See for example Why isn't FANBEAM linear? or Radon Transform works unexpectedly. Moreover, the toolbox still provides tomographic projectors only for 2D imaging not 3D, even though 64-bit RAM has made volumetric imaging commonplace in Matlab for at least 10 years. Luckily, there are now freely available 3rd party alternatives like TIGRE.

Muhammad
Last activity about 22 hours ago

Transfer Function to State Space Using Prediction Error Method

Hi Everyone,

I have Experiemental Data (Bode Plot), using MATLAB I found the Transfer Function of my plant. I have attached my E7i_CSV file.

T2 = readtable('E7i_CSV.csv');   
                                                                       % Fill With Actual Sampling Frequency
FHz = T2.F;
Ts = 1/(2*(max(FHz)+10000))
for k = 1:size(T2,1)-1
    if FHz(k+1) == FHz(k)
        FHz(k+1) = FHz(k+1)+0.5;                                                % 'Brute Force' Interpolation 
    end
end
Mag = T2.G;
PhDeg = T2.P;
Response = Mag.*exp(1j*deg2rad(PhDeg));                                         % Complex Vector
sysfr = idfrd(Response, FHz, Ts, 'FrequencyUnit','Hz')
%bode(sysfr)
%tfsys = tfest(sysfr,4,3) This is much better
tfsys = tfest(sysfr,4,3) %82.69%
%tfsys = tfest(sysfr,6,3)
figure
compare(sysfr, tfsys)
is_stable = isstable(tfsys);
disp(is_stable);

I want to convert this transfer function to statespace equations, which will be used for Model Predictive Control Design. Simple tf2ss command give me TF but it doesn't look very accrurate.

[A, B, C, D] = tf2ss(num,den)

So, I was reading a paper which i will follow, they have mentioned that they had FRF (Frequency Response Function) data and they find state space model/equations using Prediction Error Method (PEM). But I am unable to understand how I can used Bode Plot data and convert it state space using PEM. I will appreciate your help.

Secondy I verified the paper StateSpace Model by first converting it to Transfer Function and then using tf2ss command. which shows inaccurate results similiar to my results. I am looking for your help. Following is the verification code for paper i am following

%Rana Paper State Space Equations Coversion to
                            %Transfer Function for Validation Reason
% Define state-space matrices
Ax = [-49.3277, -980.7648, 618.2198;
      567.3557, -120.2273, 651.7342;
      -45.8885, -415.4194, -115.7522];
Bx = [-1.8122; 3.901370; 4.3011];
Cx = [14.9368, 16.9208, -23.6827];
Dx = 0;
% Create a state-space model
sys = ss(Ax, Bx, Cx, Dx);
% Display the state-space model
disp('State-Space Model:');
disp(sys);
% Convert the state-space model to a transfer function
tf_sys = tf(sys);
% Display the transfer function
disp('Transfer Function:');
disp(tf_sys);
                        %TF to StateSpace Rana Model
num_rana = [ -62.92 3.625*10^4 -1.065*10^8];
den_rana = [ 1 285.3 8.811*10^5 1.982*10^8];
tff_rana = tf(num_rana,den_rana);
tffss_rana = tf2ss(num_rana,den_rana);
[Arana,Brana,Crana,Drana] = tf2ss(num_rana,den_rana);

https://thingspeak.com/channels/2278931

Shore
Last activity about 10 hours ago

Halloween Analysis using Thingspeak

Halloween Analysis of Many Aspects of Halloween Headquarters and Effects on USA

(Note to Chistopher: I used a simple ESP8266 generating random numbers for fields 1 thru 7, (0 to 100, 4000, 127, 30, 45, 200,000, 50,000) and 0 to 1 for field 8. And a couple of real sensor inputs.

Halloween Analysis

goc3
Last activity about 3 hours ago

Don't Reinvent the Wheel

Have you ever learned that something you were doing manually in MATLAB was already possible using a built-in feature? Have you ever written a function only to later realize (or be told) that a built-in function already did what you needed?

Two such moments come to mind for me.

1. Did you realize that you can set conditional breakpoints? Neither did I, until someone showed me that feature. To do that, open or create a file in the editor, right click on a line number for any line that contains code, and select Set Conditional Breakpoint... This will bring up a dialog wherein you can type any logical condition for which execution should be paused. Before I learned about this, I would manually insert if-statements during debugging. Then, after fixing each bug, I would have to delete those statements. This built-in feature is so much better.

2. Have you ever needed to plot horizontal or vertical lines in a plot? For the longest time, I would manually code such lines. Then, I learned about xline() and yline(). Not only is less code required, these lines automatically span the entire axes while zooming, panning, or adjusting axis limits!

Share your own Aha! moments below. This will help everyone learn about MATLAB functionality that may not be obvious or front and center.

(Note: While File Exchange contains many great contributions, the intent of this thread is to focus on built-in MATLAB functionality.)

Moja
Last activity on 13 Oct 2023 at 19:09

caret on macbook pro

The carot symbol on my keyboard (ˆ shift+6) doesn't work on matlab. Matlab doesn't recognize it so I can't write any equation with power symbol. I tried every possible solution on the web and it doesn't work. even in the character viewer I don't have any result when I search ''caret".

https://www.mathworks.com/academia/student-challenge/simulink-student-challenge-2023.html

Ben Pasquariello
Last activity on 13 Oct 2023 at 11:07

Simulink Student Challenge 2023 is live!

Exciting news for students! 🚀Simulink Student Challenge 2023 is live! Unleash your engineering skills and compete for exciting rewards. Submission deadline is December 12th, 2023!

Ideas

Chen Lin
Last activity on 14 Oct 2023 at 0:47

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.

Highlights

Toshiaki Takeuchi
Last activity on 12 Oct 2023 at 14:23

YouTube livestream: "What's New in R2023b" coming up in a few hours!

Adam and Heather will be discussing new features in R2023b and answering your questions in a few hours - visit the link below to check out the preview and sign up for notification.

https://www.youtube.com/watch?v=mImQs4PfioM

Ideas

Chen Lin
Last activity on 11 Oct 2023 at 17:35

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

Highlights

Toshiaki Takeuchi
Last activity on 11 Oct 2023 at 1:03

Introducing Adam Danz's new Blog on MATLAB Graphics and App Building

Adam Danz just launched a new blog about MATLAB Graphics and App Building.

https://blogs.mathworks.com/graphics-and-apps/2023/10/10/welcome/

As you know, He has been a prolific contributor to MATLAB Answers and one of his answers recently won the Editor's Choice Award.

If there are any topics or questions you are interested in, please share with Adam, and I am sure he will get those into his blog.

Adam Danz
Last activity on 13 Oct 2023 at 22:04

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 on 12 Oct 2023 at 18:09

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 on 10 Oct 2023 at 17:42

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 on 10 Oct 2023 at 17:41

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 on 7 Oct 2023 at 3:54

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 on 10 Oct 2023 at 5:49

"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 on 5 Oct 2023 at 2:27

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 on 3 Oct 2023 at 21:38

The new release is here!

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

Mike Croucher
Last activity on 4 Oct 2023 at 21:22

spy easter egg

spy