How do I define a variable without assigning it a value?
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I just want to define a variable, f without assigning any values to it so I can use it in an equation.
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Star Strider
2016년 6월 16일
You can also assign a variable as an empty matrix, cell, string (or any other empty value):
x = []; % Empty Scalar, Vector Or Matrix
y = {}; % Empty Cell
z = ''; % Empty String Or Character
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Rik
2022년 9월 2일
What is your issue with that? It creates an empty array of the uint8 datatype, exactly as was asked.
Walter Roberson
2022년 9월 2일
"exactly" what was asked was "without assigning any values to it so I can use it in an equation"
Assigning an empty array to a variable is assigning a value to it (the empty value), and does not form something that can be used to create equations (in the sense of being able to solve or numerically solve the equation)
The supported answers to create something to be used in "equations" include
- Symbolic Toolbox -- sym() and syms()
- Problem Based Optimization -- optimvar()
- I am fairly unclear on the details, but maybe Deep Learning "dlarray" might arguably qualify in this category? https://www.mathworks.com/help/deeplearning/ref/dlarray.html ??
추가 답변 (5개)
Lucas Hilden
2020년 1월 22일
have no clue
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James Tursa
2020년 11월 12일
MATLAB is a dynamically typed language. You create the variable by assigning it a value. You don't need to create or type it ahead of time like you do in compiled languages such as C/C++.
Walter Roberson
2020년 1월 22일
You can use James' File Exchange contribution https://www.mathworks.com/matlabcentral/fileexchange/31362-uninit-create-an-uninitialized-variable-like-zeros-but-faster to create an uninitialized array. The initial contents of the variable will be whatever happened to be in memory,
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Walter Roberson
2021년 12월 12일
If you are trying to set up an optimization problem, sometimes it is easier to do it by expressing relationships between variables. You might be able to take advantage of Problem Based Optimization
In some cases, equations that you might not think of normally as being optimizations can be rewritten: the expression A(x) == B(x) can potentially be rewritten in terms of minimizing (A(x)-B(x))^2, so if you have the Optimization Toolbox but not the Symbolic Toolbox, then this approach has some potential.
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Hoang Truong
2023년 3월 19일
syms theta;
R=[cos(theta) sin(theta)];
>> R
R = [cos(theta), sin(theta)]
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