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David
David
Last activity 2020 年 2 月 12 日

January 2020 release notes

The following is a list of updates and new features for MATLAB Central, including MATLAB Answers, File Exchange, Blogs, and Cody.

New Features

Profile search - A global community profile search has been added. The search field on community profile pages has been updated from a standard content search to a user profile search. This improvement makes it easier to find community members across all MATLAB Central. Previously one had to search the Answers contributors , File Exchange authors , and Cody players page when looking for a user profile.

Last seen - We have added a 'last seen' timestamp to community profiles which displays the date of a person's last visit to MATLAB Central. This can be a relevant bit of information and help determine how recent someone has been active in the community.

Answers pages design update - Answers Q&A pages have been updated to remove extra white space. This update includes smaller sized avatars, and position changes for the voting and content actions among other small changes. All these changes also help improve the mobile experience as well.

Original poster styles - Original poster styles have been introduced in Answers. When a question author participates in a Q&A thread their comments or answers will be styled with a blue background and left border so they're easily discernable from other contributors.

File Exchange data in monthly emails - File Exchange stats will be included in the monthly email we send to contributors who've participated in the community on any given month.

Trending content algorithm - The MATLAB Central home page trending content algorithm has been updated to look at content activity over a shorter period of time resulting in a more dynamic feed.

Walter Roberson does it again by winning the coveted MOST ACCEPTED answers badge for all his contributions in MATLAB Answers this past year. Walter has won this badge every year since 2015. It was way back in 2014 when Image Analyst out paced Walter and was awarded the badge.

There are 10 community members who have achieved the Top Downloads badge for their popular File Exchange submissions in 2019. Do you recognize any of these names? There's a good chance you've used one or more of their toolboxes or scripts in your work if you're a frequent visitor to File Exchange, if you're not you might want to check out what they've posted, it may save you a lot of time writing your own code.

--------------------- Top Downloads Badge Winners -----------------

Congratulations to all these winners and a giant THANK YOU for all they've done this past year to help everyone in the MATLAB Central community!

David
David
Last activity 2020 年 1 月 21 日

Introducing File Exchange badges

We are happy to announce that virtual badges can now be achieved for participating in MATLAB Central File Exchange . We have 30 badges that anyone can achieve, which will also boost your community profile. Some badges are relatively simple to get while others will depend on how useful your submissions are to others in the community. Check out Ned Gulley's blog post for a great introduction.

Explore resources, ask questions, and discuss topics related to using Simulink to apply power electronics control to Electric Vehicles, Renewable Energy, Battery Systems, Power Conversion, and Motor Control. This is the 3rd MATLAB Central community, after Maker and SimBiology , and is moderated by Tony Lennon . Tony is the Power Electronics Marketing Manager at MathWorks.

Visit the community here . As always, let us know what you think by liking this post or commenting below.

Hi, I'm trying to solve this problem but I'm getting an error so far.
Problem:
Given a vector a, find the number(s) that is/are repeated consecutively most often. For example, if you have
a = [1 2 2 2 1 3 2 1 4 5 1]
The answer would be 2, because it shows up three consecutive times
What I've written so far (not done):
a = [1 2 2 2 1 3 2 1 4 5 1];
[x,y] = size(a);
counter = zeros(1,10);
if x == 1
for i=1:1:y
if a(i) == a(i+1)
counter(a(i)) = counter(a(i))+1
end
end
else
for i=1:1:x
if a(i) == a(i+1)
counter(a(i)) = counter(a(i))+1
end
end
end
But it says "error" in the line of "if a(i) == a(i+1)". I noticed that it creates a variable called "i" which value is 11, but it should create a vector from 1 to 11. What's wrong here?
I know my solution might not be in the right direction or something, but please don't tell me anything!
Thanks in advance
Rik
Rik
Last activity 2022 年 11 月 4 日

How to create a GUI

There are multiple ways to create a graphical user interface (GUI) in Matlab. Which method is the best depends on multiple factors: the complexity of the project, to what extent it should be a long-term solution, on what releases your GUI should work, your available time, your skill level, and probably other factors I'm forgetting.
To keep the thread clear I'll attempt to provide a short outline a few ways in this question, and leave the details for the answers. (@anyone with editing privileges: feel free to update the section below if I missed something important and am slow in editing this question)
---------------------------------------------------------------------------------------------------
GUIDE
GUIDE is probably the first tool new users will encounter. It is very useful for quickly putting something together, but it is otherwise fairly limited. It requires maintaining (and distributing) both a .m and a .fig file. Note that the GUIDE environment will be removed in a future release. After GUIDE is removed, existing GUIDE apps will continue to run in Matlab but they will not be editable in GUIDE. If you're starting a new GUI, don't use GUIDE. If you're updating an existing GUIDE GUI, migrate it to AppDesigner. In R2021a the first step for this removal was taken: all templates except the blank template have been removed.
GUILT
Although I haven't had a detailed look myself, it seems a list like this is not complete without at least mentioning the GUI Layout Toolbox, which is available on the file exchange and offers a lot of customization options.
Programmatic GUIs
You can bypass GUIDE and use the normal figures and functions like uicontrol to build GUIs from code. This makes the design less visual, but more flexible for future additions.
App Designer
The official successor to GUIDE, AppDesigner is not based on functions, but works similar to a class. It uses uifigure and mostly uses graphical elements that are incompatible with 'normal' GUIs that are created with a figure (or .fig).
Dear Sir or Madam
I tried to solve the cody-problem namend in the title.
Could you pleas tell me how I should name the vektor/variable in which it should be presentet?
Thank you for helping me.
Yours faithfully
Jann Borlinghaus
I wrote a Cody problem, but I want to prevent people from using tricks to get a false "best" solution.
For example, many people do something like the following:
regexp '' '(?@"CODE HERE)';
in order to get the size of their program down to something quite small. I want to prevent this. I have seen people using some weird tests to try to block this, but I don't know how they work and when I try to copy them they fail.
Alejandro Carabe-Fernandez
Alejandro Carabe-Fernandez
Last activity 2020 年 11 月 11 日

Matlab Academy and Cody

Would it make sense that, in order to enhance coding experience with practice exercises, each section of the Matlab Academy courses reference specific CODY problems related to that section so the CODY problems can be used in parallel with the structure of the Matlab Academy courses?
Nick
Nick
Last activity 2016 年 11 月 27 日

How do I know the size of a solution in Cody?

I started with Cody today and I found the file calculateSize.m https://de.mathworks.com/matlabcentral/fileexchange/34754-calculate-size which should determine the size of my solution. Unfortunately I do not get it to run. Can someone explain this to me or maybe explain how exactly the size of the solution is calculated?
Summary:
Dynamically accessing variable names can negatively impact the readability of your code and can cause it to run slower by preventing MATLAB from optimizing it as well as it could if you used alternate techniques. The most common alternative is to use simple and efficient indexing.
Explanation:
Sometimes beginners (and some self-taught professors) think it would be a good idea to dynamically create or access variable names, the variables are often named something like these:
  • matrix1, matrix2, matrix3, matrix4, ...
  • test_20kmh, test_50kmh, test_80kmh, ...
  • nameA, nameB, nameC, nameD,...
Good reasons why dynamic variable names should be avoided:
There are much better alternatives to accessing dynamic variable names:
Note that avoiding eval (and assignin, etc.) is not some esoteric MATLAB restriction, it also applies to many other programming languages as well:
MATLAB Documentation:
If you are not interested in reading the answers below then at least read MATLAB's own documentation on this topic Alternatives to the eval Function, which states "A frequent use of the eval function is to create sets of variables such as A1, A2, ..., An, but this approach does not use the array processing power of MATLAB and is not recommended. The preferred method is to store related data in a single array." Data in a single array can be accessed very efficiently using indexing.
Note that all of these problems and disadvantages also apply to functions load (without an output variable), assignin, evalin, and evalc, and the MATLAB documentation explicitly recommends to "Avoid functions such as eval, evalc, evalin, and feval(fname)".
The official MATLAB blogs explain why eval should be avoided, the better alternatives to eval, and clearly recommend against magically creating variables. Using eval comes out at position number one on this list of Top 10 MATLAB Code Practices That Make Me Cry. Experienced MATLAB users recommend avoiding using eval for trivial code, and have written extensively on this topic.
Gregory
Gregory
Last activity 2017 年 6 月 13 日

Matlab webread (or urlread) Cody

Something seems to either have changed with webread/urlread behavior with R2016a or the Cody site has changed its authentication after it's September 2016 upgrade. Now, when ever I make a call using either webread (with weboptions) urlread using "My Cody" url, I get the html that corresponds to an unauthenticated user.
Ex: https://www.mathworks.com/matlabcentral/cody/players/1261697-gregory/solved
I've tried passing credentials using weboption and also cached the credentials using the built in Matlab browser - neither helped in seeing the authenticated version of this page.
Any help in understanding where the problem/solution lies would be helpful. Easily reproduced by running...
URL = 'https://www.mathworks.com/matlabcentral/cody/players/1261697-gregory/solved';
[Contents Status] = urlread(URL);
Compare this to the source pulled down when authenticated with Chrome (for example, search for the work "two"). FYI: this has worked for a couple of years up until now...
O45
O45
Last activity 2018 年 10 月 23 日

Best solution to cody problems

Hi, I am uploading the answers to cody problems. Although most of answers are correct but my size is bigger than the best answer. How can I view the best answer?
The community is very helpful, yet I feel really powerless that I cannot find the appropriate way to code, nor find the problems with the codes I have written. I have read numerous books on MATLAB, mostly related with science and engineering applications. Any advice to improve would be greatly appreciated. Thanks.
James
James
Last activity 2015 年 6 月 11 日

Issue with Cody Challenge Badges?

Apologies for putting this question here, but I'm not sure there's a specific forum for Cody-related questions.

I recently noticed that a new badge for "Magic Numbers Master" had been created and awarded. When I entered my profile to check that out, I noticed that I had received that badge, but lost the badge for "Cody Challenge Master." I thought that maybe my solution had been messed up because of a change in one of the test suites that my solution missed, as this has happened a number of times on other problems. According to the text underneath the badge icon, I've still solved all 96 of the questions in the Cody Challenge. All of the problems listed as part of that challenge are still marked as "Solved." Has anyone else run into this issue?

Andrew Newell
Andrew Newell
Last activity 2017 年 4 月 23 日

Why doesn't Cody accept a class definition?

I created a solution for Cody Problem 1745 (Get me!) that is very simple and works perfectly on my computer; but in Cody, it results in the error:
Error: Undefined function or variable 'me'.
The test code is:
get = me();
y = rand(1,12345);
!rm now.m
!rm assert.m
assert(get == now)
My solution is:
classdef me
methods
function tf = eq(obj,~)
tf = true;
end
end
end
Why doesn't Cody accept this?
(P. S.) And why doesn't it accept function definitions like
function justDoIt
(which are appropriate for some problems and accepted by MATLAB) but requires at least one input and output?
if i want write fewer codes in cody,what should I pay attention to?
Can anyone explain how Cody calculates the size of a program?
I read the help, but couldn't understand. :(
Why cody does not allow 'eval', 'evalc','feval' etc functions in the solutions? What is alternative to these functions?
e.g. I need to use:
if f='3*x'
x=0:10;
y=eval(vectorise(f))
so that values of y can be calculated as 3.*x
bt cody does not let us to use functions like eval
What is the alternative?
I have been stuck in the Cody question: Problem 31. Remove all the words that end with "ain"
http://www.mathworks.com/matlabcentral/cody/problems/31-remove-all-the-words-that-end-with-ain
for the whole afternoon. My codes below passed the first two tests but failed in the third one, because my codes cannot separate "" and ain. Anyone could help?
function s2 = remAin(s1)
s1_cell = strread(s1, '%s');
[s1_cell{find(not(cellfun('isempty', regexp(s1_cell, '\w*ain\>'))) == 1)}] = deal(' ');
s2 = strjoin(s1_cell');
s2 = strrep(s2, sprintf('%c%c%c', 32,32,32), sprintf('%c%c', 32,32));
if s2(end) == ' ' && s2(end-1) == ' '
s2(end) = [];
end
end