# Use workspace variable in equation solver

4 views (last 30 days)
Ahmed Abdulla on 9 Aug 2022
Answered: Walter Roberson on 9 Aug 2022
I have the equation x+y=25 and currently I have y as a predfined variable=5. so the equation becomes x+5=25. However I would like to change y from my script and the equation to automatically change based on my y value rather than me modifying my equations each time to edit the y value.
I currently do it this way:
y=5;
syms x
eqn = x+5=25;
S = solve(eqn,x);

Rik on 9 Aug 2022
If you don't want to use a function to wrap the input, you can use an anonymous function instead.
y=5;
syms x
eqn =@(y) x+y==25;
S = solve(eqn(y),x)
S =
20

Walter Roberson on 9 Aug 2022
syms x y
eqn = x + y == 25
eqn =
y = 5
y = 5
subs(eqn)
ans =
y = 9
y = 9
subs(eqn)
ans =

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