How do I define a variable without assigning it a value?

조회 수: 1,381 (최근 30일)
Ethan Sehrt
Ethan Sehrt 2016년 6월 16일
답변: Hoang Truong 2023년 3월 19일
I just want to define a variable, f without assigning any values to it so I can use it in an equation.
  댓글 수: 3
João Santos
João Santos 2021년 12월 12일
without syms, whats the best option?
Image Analyst
Image Analyst 2021년 12월 12일
@João Santos, see Star's answer below.

댓글을 달려면 로그인하십시오.

채택된 답변

Star Strider
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
  댓글 수: 5
Rik
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
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

댓글을 달려면 로그인하십시오.

추가 답변 (5개)

Lucas Hilden
Lucas Hilden 2020년 1월 22일
have no clue
  댓글 수: 2
James Tursa
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++.

댓글을 달려면 로그인하십시오.


Azzi Abdelmalek
Azzi Abdelmalek 2016년 6월 16일
You can use a Symbolic Math Toolbox http://www.mathworks.com/help/symbolic/index.html

Walter Roberson
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,

Walter Roberson
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.

Hoang Truong
Hoang Truong 2023년 3월 19일
syms theta;
R=[cos(theta) sin(theta)];
>> R
R = [cos(theta), sin(theta)]

카테고리

Help CenterFile Exchange에서 Symbolic Math Toolbox에 대해 자세히 알아보기

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by