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James
James
Last activity il 11 Giu 2015

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?

NOTE: this discussion is continued at MATLAB Answers Wish-list #6 (and bug reports)
I've opened MATLAB Answers this morning and found the new design.
The field for typing the "Body" does not consider the font settings of my browser anymore, such that my preference of sans-serif fonts is ignored. In addition the text color is a medium gray, which is hard to read for me due to the too light contrast.
Blank lines in the code let two separate code boxes appear. This makes almost all code, I've posted in the forum, invalid. It has been discussed repeatedly, that blank lines in the code confuse the indentation of the display in the forum and that this is a really bad idea. But instead of improving this, it is made severely worse now.
The new design contains even more white space, such that standard questions cannot be answered without extensive vertical scrolling. It is a very bad drawback, that I cannot see the question while I type the answer.
There is still no suggestion to use a proper code formatting, such that I have to spend 20% of my forum time typing corresponding comments as before.
But I'm coming back to the most important problem for me: It is a physical problem for me to read the low contrast grey on white text. Does anybody know a tweak or CSS trick to increase the readability?
TMW, please take into account that this new design is physically hard to read for people without young and 100% perfect eyes. This is very annoying for me.
Splitting code blocks at white lines is simply a bug. I cannot imagine why this error has not been detected before the new design has been published. The argument, that TMW is extremely conservative with changes in the forum to ensure a stability does not convince me anymore.
[EDITED] The box around the thread, the preview box, the boxes for preformatted text and code have a grey background now. So some text is even medium grey on light grey.
I'd be glad if the designers refocus on the purpose of the forum. Whatever this purpose might be, the optical reception of the characters is fundamental.
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
Sven
Sven
Last activity il 7 Lug 2023

What's on your personal MATLAB to-do list?

What MATLAB tools or functions have you been thinking about making but haven't quite gotten around to it?
It can be something specific to your work if you'd like, but it's preferably:
  • the kind of tool or task that we don't really expect in the next MATLAB release (ie., not a frequent entry in a MATLAB wishlist)
  • something that would be useful to you and (hopefully) others if it existed.
  • something that could conceivably be made by people(s) in the user community
Think of it maybe as a file exchange wishlist.
Votes for good ideas . I guess you'll get more votes if it's an idea others want to see made as well.
Probably no single accepted answer, but it would be nice to see what people have thought about and maybe we can bring a few ideas to fruition (or find that someone's already done it)
For example:
  • I've been wanting to write an object-oriented replacement for the NURBS toolbox which is a great toolbox but is very unwieldy to use.
Salam,
While I was playing with Cody, I found one interesting question that asked to write MATLAB function to create times-table (can be found here: http://bit.ly/1cWZGGM ). The question itself was easy, but I had problems to figure out how could someone solve this problem with compact code of size 10 !!
After I've checked the leading answer, it seems to be written in Chinese not in MATLAB :)
Here is the answer:
function m = timestables(n)
regexp '' '(?@A=repmat([1:n]'',1,n);m=A.*A'';)'
end
Could anyone translate this to me so that I can use it in my future attempts ? :P
Regards.
In a previous Q & A, Jan Simon pointed to Cody: Sum 1:2^n. The current leading solution to that problem has node-count (or more simply, "length") 10. Apparently, 10 is the minimal length (per the official length-function on File Exchange) of any function taking input & generating output:
function y = test_cody_solution(x)
y = x;
end
Per Cody instruction examples, additional computation within a function definition increases the solution length. For example, both of the following functions have length 12:
function y = test_cody_solution(x)
y = [x];
end
function y = test_cody_solution(x)
y = x+1;
end
My question is: what kinds of ninja-style coding idioms even exist in MATLAB which actually perform definite computation but at the same time do not increase the node-count above 10? I'm not able to imagine what could be going on in order for someone to solve a given non-trivial Cody puzzle in length 10 or 11? IOW, without respect to any particular Cody problem, could someone please give an example of a non-trivial function which somehow comes in at or just above the absolute lower bound? Any explanation of the magic would be appreciated as well.
Thanks, Brad
Jan
Jan
Last activity il 9 Ago 2013

Magic strings and numbers in Matlab

Some of Matlab's toolbox functions are affected by magic strings or magic numbers, which are strings or numbers with a deeper meaning besides the normal value. Both are considered as bad programming patters, because they provoke confusions, when the magic keys appear with the normal meaning by accident. See http://en.wikipedia.org/wiki/Anti-pattern
Example 1:
clear('myVariable')
clear('variables')
While the 1st clears the variable myVariable, the later clears all variables. Here 'variables' has a meta-meaning. The problem appears, when 'variables' is an existing variable:
a = 1;
variables = 2;
clear('variables')
disp(a) % >> 1
Only variables is cleared, which cannot be understood directly when its definition is 1000 lines before.
Example 2:
uicontrol('String', 'default')
This creates a button with the empty string '' instead of the expected 'default', because this is the magic string to invoke the default value get(0, 'DefaultUIControlString'). The same concerns properties of other graphic objects also, e.g. the 'name' property of figure or the string of uimenu. There is a workaround which allows the user to display 'default': Simply use '\default'. Unfortunately this is doubled magic, because in consequence it is impossible to display the string '\default'. Obviously a bad idea.
Example 3:
Graphic handles are doubles (although gobject of the new R2013a seems, like this is subject to changes? [EDITED: Yes, it changed with HG2 in R2014a]). But then a handle can be confused with data:
a = axes; % e.g. 0.0048828125
plot(a, 2, '+')
But you cannot draw the point [0.0048828125, 2] by this way, because the 1st input is considered as handle of the parent. Here all possible values of handles are magic. Collisions are very unlikely, but there is no way to avoid them reliably - as long as handles have the type double.
Question:
Which functions are concerned by magic values? What are the pitfalls and workarounds?
function b = most_change(a)
a(:,1)=a(:,1)*0.25;
a(:,2)=a(:,2)*0.1;
a(:,3)=a(:,3)*0.05;
a(:,4)=a(:,4)*0.01;
d=sum(a,2);
c=max(d);
for i=1:length(d)
if d(i)==c
b=i;
end
end
i got wa please explain idont understand
I would like to receive your feedback:
  • would you find useful to have spellcheck built into the MATLAB Editor?
(Consider also an associated toggle, positioned somewhere in the Editor, that would enable/disable the spellcheck for selective use)
Lately, I am writing many quick analyses for publish() and I find that first publishing to MS Word (to check the spelling) and then re-publishing to .html, after manual corrections, disrupts the working.
IMHO, the idea to include spellcheck into the editor would be consistent with the renewed visibility of the PUBLISH tab.
Matt Fig
Matt Fig
Last activity il 23 Feb 2023

Share your favorite snippet or utility

I am wondering what others use for those little short-cuts or niceties in MATLAB. I have in mind something you wrote or something somebody else wrote or an underused MW function.
Here are my two favorites.
This is a simple script I use. Here is the entire contents of CLC.m (yes, it is capitalized):
clear all,close all,clc
Very simple, but I use it all the time. Here is another one I use so often that I forget not every machine has it (though every machine should, IMO):
whats
Here is an underused MW function that I occasionally employ when working on someone else's machine. The usual response is, "Wait, what did you just do?"
home
What are some of yours?
Given a tic tac toe board:
1 represents X
0 represents empty.
-1 represents O
It is X's move. If there is an immediate win possibility, choose a square for an immediate win. Otherwise return 0.
Return absolute index of the square of choice. If multiple square are valid, return them in order.
Example:
Input a = [ 1 0 1
-1 1 0
0 -1 -1]
Output wins is [4 8]
Can anyone explain it in detail?
I'm confused with the sentence I marked ans bold style.
Thanks a lot~~~
I've written a valid answer to the last Cody problem, but it is not even close to the best answer. I have no idea how they made this short answer. To unlock it I need to solve another Cody question, but there are none left... :(
Anybody know how to unlock the last question?
Hi,
i'm "solving" number 30 cody's problem.
I think to solve that whit sortrows function.
If I have a z vector:
j = sqrt(-1);
z = [-4 6 3+4*j 1+j 0];
my funtion is:
function z = complexSort(z)
z(2,:)=sqrt(real(z).^2+imag(z).^2);
z=sortrows(z',-2);
z=z(:,1);
end
End it return the result
z =
6.0000 6.0000
3.0000 - 4.0000i 5.0000
-4.0000 4.0000
1.0000 - 1.0000i 1.4142
0 0
The question is: why imagine part in input is positive e sortrows trasform it in negative?
best regards
Marco
NOTE: this discussion is continued at MATLAB Answers Wish-list #6 (and bug reports)
This topic is for features you would like to see for the MATLAB Answers facility itself, and also for bug reports about the MATLAB Answers facility.
This topic is the follow on to the earlier Wish-list for MATLAB Answer sections. That topic grew large enough to become unwieldy; and Mathworks has made enough changes to make a number of the past points no longer of relevance. There was also a more limited purpose <http://uk.mathworks.com/matlabcentral/answers/216662-new-design-of-the-forum-grey-on-white-wish-list-3-bug-reports
I suggest one wish (or bug report) per answer, so that people can vote their wishes.
Adam Kaas
Adam Kaas
Last activity il 6 Giu 2012

Coolest things MATLAB can do

As I'm becoming more and more familiar with MATLAB, I'm starting to fall in love with it. I was wondering what are the coolest things that you all know MATLAB can do? As for me so far, the auto-code generation into another language is the coolest thing.