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What MATLAB functions are underappreciated?

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Chad Greene
Chad Greene el 22 de Abr. de 2021
Respondida: Benjamin Großmann el 28 de Mayo de 2021
Open question: What MATLAB function(s) do you wish you had discovered sooner? Are there any functions that no one talks about, but you use every day?
There are certainly some hidden gems that I don't know about, so rather than leaving it to chance that I might find them someday by accident, share 'em now. I'll get things started with a couple of functions that I find particularly useful.

Respuestas (8)

Chad Greene
Chad Greene el 22 de Abr. de 2021
One of the most powerful functions I know of took me years from hearing about its existence to using it regularly, because it's not very intuitive to use. But ever since I learned how to think like accumarray, I have felt like I have a kind of power that's usually reserved for gods.
  5 comentarios
Steven Lord
Steven Lord el 22 de Abr. de 2021
Cell arrays were introduced in MATLAB 5.0 I think. [That was well before I started working at MathWorks.] The accumarray function is newer than cell arrays. I want to say MATLAB 6.5, but I'm not certain.
Rik
Rik el 22 de Abr. de 2021
accumarray is mentioned in the new features summary of R14SP3 ("The accumarray function now allows more flexibility for input/output classes and functions to be called."), but is missing from R13, so I presume it was added in v7.0.

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Jan
Jan el 22 de Abr. de 2021
Editada: Jan el 22 de Abr. de 2021
dbstop . Many newcomers mention, that they do not understand, what their code does. The possibility to step through it line by line after setting a break point is essential for professionals also.
Setting conditional breakpoints in all lines of a function, helps to track, where a variable is changed:
function bruteDBOnCondition(mFile, Cond)
% INPUT:
% mFile: Name of the M-file
% Cond: Char vector containing a condition, e.g. x~=0.
% The debugger stops, if the condition is TRUE.
CStr = strsplit(fileread(mFile), '\n');
[~, mName] = fileparts(mFile);
for k = 1:numel(CStr)
if ~isempty(CStr{k}) && ~startWidth(strtrim(CStr{k}), '%')
dbstop('in', mName, 'at', sprintf('%d', k), 'if', Cond)
end
end
end
Further useful applications:
dbstop if error
dbstop if all error % or: if caught error
  4 comentarios
Rik
Rik el 23 de Abr. de 2021
I should have known there was an easy way to do this. Thanks for the suggestion. This seems to cover all of my use cases, without having to resort to a 100 character line.
Jan
Jan el 24 de Abr. de 2021
It is useful, that clear all does not clear the break points in modern Matlab versions anymore.

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Chad Greene
Chad Greene el 22 de Abr. de 2021
I rarely see anyone use the lighting functions, but they're incredibly powerful and can make data come to life. They're provide a physical intution not only for surface data, but for almost any type of gridded data. For example, here's a surface without lighting:
figure
surf(peaks(1000))
shading interp
And here's the same surface with lighting:
figure
surf(peaks(1000))
shading interp
camlight
material dull
  1 comentario
Sean de Wolski
Sean de Wolski el 22 de Abr. de 2021
I like the actual light object. It's actually fairly intuitive "I want to put a green light here" and allows you do cool things like the mathworks logo (>>edit logo)

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Sean de Wolski
Sean de Wolski el 22 de Abr. de 2021
onCleanup - I want to reliably do this thing at the end... I've actually gotten to the point that I will pass these (or cell arrays on them) as return outputs to functions or properties of a class as a means to save something as long as necessary. E.g:
[filename, deleter] = someFunctionThatWritesATempFile(stuff)
filename = tempname+".csv";
writetable(stuff, filename)
deleter = onCleanup(@()delete(filename))
Now if I want the file to be temporary - just call it without an input. If I need that file to exist until I'm done with it (e.g. report gen output or something, keep the deleter around and then it still goes away at the end).

Bjorn Gustavsson
Bjorn Gustavsson el 22 de Abr. de 2021
Just a couple of basic ones:
  • lscov - linear regression when there is a data-covariance-matrix
  • svd (to use together with Tikhonov-regularization instead of pinv - every time!)
Of of the file exchange:
To be continued...
  1 comentario
Steven Lord
Steven Lord el 22 de Abr. de 2021
If you like the factorize File Exchange submission, you may be interested in the decomposition function that has been included in MATLAB for several releases.

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Sean de Wolski
Sean de Wolski el 22 de Abr. de 2021
Editada: Sean de Wolski el 22 de Abr. de 2021
mfilename I use this all of the time for building relative file or folder paths. I want currentProject().RootFolder to replace it as that's generally better but that's not supported in Compiler workflows so mfilename it continues to be.
  1 comentario
Jan
Jan el 22 de Abr. de 2021
Yes, this has been useful for projects, which stores data in subfolders of the M files:
myPath = fileparts(mfilename('fullpath'))

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Sean de Wolski
Sean de Wolski el 22 de Abr. de 2021
tempname/tempdir - Need to write something and guarantee write permissions on any platform...
  1 comentario
Rik
Rik el 22 de Abr. de 2021
The only downside is that it isn't persistent, which is where this comes in.

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Benjamin Großmann
Benjamin Großmann el 28 de Mayo de 2021
arguments declaration within functions, introduced in 2019b, is very powerful (pythonic? ;-)) for writing generic and reusable functions. Argument validation is great, but I really enjoy the possibility to define (additional) optional name-value argumentsn as well as the functions usage with name-value pairs and the possibitlity to define default values for input arguments.
function someFunction(invars)
arguments
invars.someInt {mustBeInteger} = rand(3);
invars.someText {mustBeText} = inputdlg('Input argument b');
end
% use invars.someInt and invars.someText within the function
% someCode
%
end
Call the function with or without any of the (optional) arguments:
someFunction(someInt=2, sometText='Text');
someFunction(someInt=2);
someFunction(sometText='Text');
someFunction();

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