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Rik
Ultima attività il 7 Feb 2024

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)
For Q&A
17%
For programming tasks
27%
For writing
9%
For fun
26%
Other use-case not mentioned here
3%
What's ChatGPT?
17%
4555 voti
MATLAB users come to Cody to learn MATLAB and the best way to learn is to learn from other community users. However, when you tried to see all solutions, you saw a message that you had to solve a new problem to unlock all the solutions or submit a solution of a smaller size. This is very confusing and we have been hearing this pain point from users.
Today, the Cody team is pleased to announce that players are able to see all solutions to a problem once they solve it correctly.
After solving a problem, you will see a button that says ‘View Community’s Solutions’, which will bring you to the list of all solutions.
Note that this is our first step in facilitating the learning aspect of Cody. We are actively working on improving the solutions list, so your input is valuable to us. Please let us know your comments or suggestions.
Yes in MATLAB
18%
Yes but only in some other language
22%
Yes in MATLAB and other language(s)
7%
Not yet but would like to learn how
34%
No & don't foresee any need to yet
19%
4243 voti
Every year, we show our appreciation to the top contributors by awarding two types of annual badges: Most Accepted badge and Top Downloads badge.
Most Accepted badge goes to the top 10 contributors whose answers received the most acceptances. Top downloads badge goes to the top 10 contributors with the most downloaded submissions.
In 2022, the recipients for Most Accepted are: @Walter Roberson, @Voss, @Star Strider, @Torsten, @Image Analyst, @Matt J, @KSSV, @Jan, @Stephen23, and @DGM.
The recipients for Top Downloaded are: @Cleve Moler, @Yarpiz, @John D'Errico, @Seyedali Mirjalili, @Rodney Tan, @Yair Altman, @Chad Greene, @Steve Miller, @Giampiero Campa, and @Scott Lowe
Congratulations and thank you again for your outstanding contribution in 2022!
MathWorks is hosting the QIT Boston event to discuss Ethical AI for the LGBTQ+ community on its Lakeside campus, hosted by our own Heather Gorr, PhD.
AI is known to learn biases from the various sources that affects our daily lives, and in particular minority groups like LGBTQ+.
Join the discussion to what the impacts are, where the biases come from, and how to mitigate as you develop AI.
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Congratulations, @DGM, for hitting this important milestone!
You provided 2,007 anwers and received 529 votes. Thank you for your contribution to the community!
MATLAB Central Team
an undergraduate student
41%
in graduate school
28%
in academia (prof, staff, etc.)
11%
in industry or Non-Gov't Org. (NGO)
11%
in government or military
3%
self employed, retired, or hobbyist
6%
7627 voti
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.
Congratulations, @KSSV, for hitting this important milestone!
You provided 10,958 anwers at the acceptance rate of 78.95% and received 3,126 votes. Thank you for your contribution to the community!
MATLAB Central Team
What amazing images can be created with no more than 280 characters of MATLAB code? Check out the GALLERY from the MATLAB Mini Hack 2022 contest.
Vote on your favorite MATLAB images before Oct. 30th! We will give out MathWorks T-shirt to 10 lucky voters.
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New in R2022b: GridSizeChangedFcn
tiledlayout() creates a TiledChartLayout object that defines a gridded layout of axes within a figure. When using the 'flow' option, the grid size becomes dynamic and updates as axes are added or as the figure size changes. These features were introduced in R2019b and if you're still stuck on using subplot, you're missing out on several other great features of tiledlayout.
Starting in MATLAB R2022b you can define a callback function that responds to changes to the grid size in flow arrangements by setting the new gridSizeChangedFcn.
Use case
I often use a global legend to represent data across all axes within a figure. When the figure is tall and narrow, I want the legend to be horizontally oriented at the bottom of the figure but when the figure is short and wide, I prefer a vertically oriented legend on the right of the figure. By using the gridSizeChangedFcn, now I can update the legend location and orientation when the grid size changes.
Demo
gridSizeChangeFcn works like all other graphics callback functions. In this demo, I've named the gridSizeChangedFcn "updateLegendLayout", assigned by an anonymous function. The first input is the TiledChartLayout object and the second input is the event object that indicates the old and new grid sizes. The legend handle is also passed into the function. Since all of the tiles contain the same groups of data, the legend is based on data in the last tile.
As long as the legend is valid, the gridSizeChangedFcn updates the location and orientation of the legend so that when the grid is tall, the legend will be horizontal at the bottom of the figure and when the grid is wide, the legend will be vertical at the right of the figure.
Since the new grid size is available as a property in the TiledChartLayout object, I chose not to use the event argument. This way I can directly call the callback function at the end to update the legend without having to create an event.
Run this example from an m-file. Then change the width or height of the figure to demonstrate the legend adjustments.
% Prepare data
data1 = sort(randn(6))*10;
data2 = sort(randn(6))*10;
labels = ["A","B","C","D","E","F"];
groupLabels = categorical(["Control", "Test"]);
% Generate figure
fig = figure;
tcl = tiledlayout(fig, "flow", TileSpacing="compact", Padding="compact");
nTiles = height(data1);
h = gobjects(1,nTiles);
for i = 1:nTiles
ax = nexttile(tcl);
groupedData = [data1(i,:); data2(i,:)];
h = bar(ax,groupLabels, groupedData, "grouped");
title(ax,"condition " + i)
end
title(tcl,"GridSizeChangedFcn Demo")
ylabel(tcl,"Score")
legh = legend(h, labels);
title(legh,"Factors")
% Define and call the GridSizeChangeFcn
tcl.GridSizeChangedFcn = @(tclObj,event)updateLegendLayout(tclObj,event,legh);
updateLegendLayout(tcl,[],legh);
% Manually resize the vertical and horizontal dimensions of the figure
function updateLegendLayout(tclObj,~,legh)
% Evoked when the TiledChartLayout grid size changes in flow arrangements.
% tclObj - TiledChartLayout object
% event - (unused in this demo) contains old and new grid size
% legh - legend handle
if isgraphics(legh,'legend')
if tclObj.GridSize(1) > tclObj.GridSize(2)
legh.Layout.Tile = "south";
legh.Orientation = "horizontal";
else
legh.Layout.Tile = "east";
legh.Orientation = "vertical";
end
end
end
Give it a shot in MATLAB R2022b
  • Replace the legend with a colorbar to update the location and orientation of the colorbar.
  • Define a GridSizeChangedFcn within the loop so that it is called every time a tile is added.
  • Create a figure with many tiles (~20) and dynamically set a color to each row of axes.
  • Assign xlabels only to the bottom row of tiles and ylabels to only the left column of tiles.
Learn about other new features
This article is attached as a live script.
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Uniform spacing and the problem of round-off error
The vector [3 4 5 6 7 8 9] is uniformly spaced with a step size of 1. So is [3 2 1 0 -1 -2] but with a step size of -1.
The vector [1 2 4 8] is not uniformly spaced.
A vector v with uniform spacing has the same finite interval or step size between consecutive elements of the vector. But sometimes round-off error poses a problem in calculating uniformity.
Take, for example, the vector produced by
format shortg
v = linspace(1,9,7)
v = 1x7
1 2.3333 3.6667 5 6.3333 7.6667 9
Linspace produces linearly spaced vectors but the intervals between elements of v, computed by diff(v), are not identical.
dv = diff(v)
dv = 1x6
1.3333 1.3333 1.3333 1.3333 1.3333 1.3333
dv == dv(1)
ans = 1×6 logical array
1 0 0 1 0 1
diff(dv)
ans = 1x5
4.4409e-16 0 -4.4409e-16 8.8818e-16 -8.8818e-16
Some extra steps are therefore necessary to set a tolerance that ignores error introduced by floating point arithmetic.
New in R2022b: isuniform
Determining uniformity of a vector became a whole lot easier in MATLAB R2022b with the new isuniform function.
[tf,step] = isuniform(v)
isuniform returns a logical scalar indicating whether vector v is uniformly spaced within a round-off tolerance and returns the step size (or NaN if v is not uniform).
Let's look at the results for our vector v,
[tf,step] = isuniform(v)
tf = logical
1
step =
1.3333
How about non-uniformly spaced vector?
[tf,step] = isuniform(logspace(1,5,4))
tf = logical
0
step =
NaN
Give it a shot in MATLAB R2022b
  • What happens when all elements of v are equal?
  • Can you produce a vector with uniform spacing without using colons or linspace?
  • What additional steps would be needed to use isuniform with circular data?
References
This article is attached as a live script.
Always or usually. They're fun.
18%
Sometimes, some of them.
7%
Not yet, but probably will some day
25%
Never, and don't plan to.
50%
3937 voti
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Grace Hopper Celebration is an event that celebrates the legacy of Grace Hopper who acted as the inspiration for generations of women in tech. My female coworkers in highly accomplished technical roles will be speaking at the event. Come meet, connect and network with them at GHC22.
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If you are interested in developing algorithms for robotics and autonomous systems using ROS, there is an upcoming livestream just for you.
In this livestream, Jose Avendano Arbelaez and Ronal George will show you how to build and deploy autonomous algorithms using ROS. Using examples, they will show how to interface with ROS networks using publishers and subscribers, build algorithms for mapping, planning and navigation and deploying algorithms as ROS nodes.
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