Define a symbolic variable and then calculate it later

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Alessandro Longo 2017-12-7

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https://ww2.mathworks.cn/matlabcentral/answers/371604-define-a-symbolic-variable-and-then-calculate-it-later

评论： Stephen23 2017-12-7

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Hello forum, I would build something like this:

my_input = 2+0.5*t;

with variable t not already defined. Then, in the same code, I would define the t vector and then re-calculate my_input with the proper values of t. I need it because in this code, the user can only modify the first section. If I declare the time variable earlier, there is the risk to be modified.

Example of what I would realize (but with syms it does not work):

 syms t
 my_input = 2+0.5*t; % t is a sort of symbolic variable
 t = linspace(0,100,1000); % now t is a real variable
 my_new_input = my_input; % but now calculated with real t values

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Stephen23 2017-12-7

"I need it because in this code, the user can only modify the first section. If I declare the time variable earlier, there is the risk to be modified."

That is not a very good reason to use symbolic math. Just design your code better by splitting it into some functions that are called by the user.

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