How to access bounds of conditions obtained from solving matlab inequalities ?

Question

Rahul Sharma 2024-2-23

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2085818-how-to-access-bounds-of-conditions-obtained-from-solving-matlab-inequalities

评论： Rahul Sharma 2024-2-24

采纳的回答： Hassaan

在 MATLAB Online 中打开

Hello,

I am trying to solve a matlab inquality for a function such as y = f(x).

using matlab vpasolver.

r = solve(y>0,x,"Real",true,'ReturnConditions', true)

Now, i obtain the solution of this inequality which looks like following.

r = 
  struct with fields:
            x: [1×1 sym]
    parameters: [1×1 sym]
    conditions: [1×1 sym]

when i access the conditions by r.conditions, i obtain

0.77726530669995618438861129106954 <= x

which is correct. I now want to use this numerical limit of 0.7772... . I am not able to acess this value from conditions. can anyone tell me how to do it ?

i tried to convert it into string as well but it didnt work.

thanks !

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Answer 1

Hassaan 2024-2-23

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2085818-how-to-access-bounds-of-conditions-obtained-from-solving-matlab-inequalities#answer_1415193

编辑：Hassaan 2024-2-23

在 MATLAB Online 中打开

syms x
y = x^2 - 3*x + 2; % Example function
r = solve(y > 0, x, 'Real', true, 'ReturnConditions', true);
% Extract the condition
cond = r.conditions;
% Assume the condition is in the form of an inequality like '0.777 <= x'
% We can convert this condition to a string and then extract the numeric part
condStr = string(cond); % Convert to string
numStr = regexp(condStr, '[\d.]+', 'match'); % Extract numeric part as string
% Now, convert the string to a numeric value
numVal = str2double(numStr{1});
disp(numVal)
     2

Note

Other approaches may also exist.

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