input equation from user

Question

Saumya 2014-4-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/127111-input-equation-from-user

回答： Mohammed Alrajeb 2019-8-9

Hi, I am a new user for MATLAB and I have R2010a version. I want to write a program where user should be able to enter euqation as input. e.g. : 5x^2 + 2x =8. And once the equation is fed in, I want to find out value of the equation for a perticular x value.

Please help.

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Answer 1

Jos (10584) 2014-4-25

5
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/127111-input-equation-from-user#answer_134538

在 MATLAB Online 中打开

str = input('Give an equation in x: ','s')  ;
   % the user types in, for instance 2*x^2-3*x+4
x = input('Type in a value of x: ') ; 
   % the user types in, for instance, 2
f = inline(str,'x') ;
y = feval(f,x) ;
disp(['"' str '", for x = ' num2str(x) ', equals ' num2str(y)]) ;

This will error when the string cannot be converted to an inline function or when the function cannot be evaluated for the value entered by the user.

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Saumya 2014-4-29

Thank you Jos,

It was really helpful.

Now going one step ahead, how can I do the same for a function with 2 variables say x and y.

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Answer 2

Manjeet Singh 2016-4-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/127111-input-equation-from-user#answer_216607

编辑：Stephen23 2016-6-24

在 MATLAB Online 中打开

str = input('Give an equation in x and y: ','s');  % the user types equation in form of x and y
f = inline(str,'x','y')   % This gives function in form of f(x,y) $ both value of x and y can be put like  f(2,3)