Rearrange Variables in an equation
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I declare the variables using sym or syms then i have an equation a+2*b=1; I want MATLAB to give me a=1-2*b; or alternatively b=(1-a)/2;
is there a way to do this?
Also, There maybe more than 2 variables Equation maybe linear or non-linear Equation can change at each iteration. Thanks
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采纳的回答
Star Strider
2012-7-20
编辑:Star Strider
2012-7-20
This is one way:
syms a b
eqn = (a + 2*b == 1)
v_a = solve(eqn, a)
v_b = solve(eqn, b)
producing this output:
v_a =
1 - 2*b
v_b =
1/2 - a/2
I suggest you avoid expressions such as:
[a b] = solve(eqn, a, b)
even though it is valid syntax, because instead of solving the equation for ‘a’ and then solving it independently for ‘b’, it solves it for ‘a’ first and then solves the resulting equation for ‘b’ in terms of an introduced variable ‘z’. That produces a multi-line warning in red (that I will not reproduce here), and the results:
a =
1 - 2*z
b =
z
that does not make sense to me. I consider this to be a bug, and I would prefer it to be an option rather than the default, but that is not my decision.
3 个评论
Star Strider
2012-7-20
This:
data = [-1 0 1;-1 +1 -1]';
alpha = sym('alpha',[1 3]);
advct = alpha * data(:,2)
v_2 = solve(advct == 0, alpha(1))
gives me these:
advct =
alpha2 - alpha1 - alpha3
v_2 =
alpha2 - alpha3
Is that the result you were hoping for?
更多回答(2 个)
Nitesh khanna
2020-8-1
how to replace the variables a, b, c, d by variables w, x, y, z for; in eqn
eqn=a+b+c+d==9;
will this command work
eqn=subs(eqn, [a,b,c,d],[w,x,y,z])
0 个评论
Bill Tubbs
2023-1-29
>> syms a b
>> eqn1 = b == (1 - a) / 2;
>> isolate(eqn1, a)
ans =
a == 1 - 2*b
>> isolate(eqn1, b)
ans =
b == 0.5000 - 0.5000*a
2 个评论
Star Strider
2023-1-29
Definitely!
I’ve used isolate extensively in my Answers since it was introduced, when its use was appropriate.
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