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

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 !

Answer 1

[Hassaan]

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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Answer 2

[Torsten]

syms x
r.conditions = 0.77726 <= x

r = struct with fields:
    conditions: 38863/50000 <= x

lhs(r.conditions)

ans = 

[Rahul Sharma]

This also works !! thank you very simple