Solving An Equation - Linear Algebra
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Hello,
I would like to solve the following equation:
eqn = Ff == Kff*uf + Kfs*us; % I want to solve for uf knowing that
Kff =
3.0240 0.7680
0.7680 3.2427
Kfs =
0 0 -1.0240 -0.7680 -2.0000 0
0 -2.6667 -0.7680 -0.5760 0 0
Ff =
0
0
us =
0
-25
0
0
0
0
The problem is that I'm getting an error from MATLAB saying that uf is not defined, uf is supposed to be a 2x1 matrix but I want to solve for it. How can I do that?
采纳的回答
Star Strider
2018-11-21
编辑：Star Strider
2018-11-22
Straightforward:
KFF = Kff \ -(Kfs*us)
KFF =
5.5556
-21.8750
Another option is to use fsolve:
[UF, fval] = fsolve(@(uf) Kff*uf + Kfs*us, [1; 1])
UF =
5.5556
-21.8750
fval =
-7.1054e-015
-14.2109e-015
5 个评论
Hazem El Sankari
2018-11-21
Hazem El Sankari
2018-11-21
编辑：Hazem El Sankari
2018-11-21
Star Strider
2018-11-21
编辑：Star Strider
2018-11-22
My pleasure.
‘But what does [1; 1] refer to at the end of the function?’
The ‘[1;1]’ is an initial parameter estimate. The fsolve function needs to have an initial guess at the value to solve for.
‘Also, what Ff was, say, [100 ; 200]?’
Ff = [100; 200]
[UF, fval] = fsolve(@(uf) Kff*uf + Kfs*us - Ff, [1; 1])
Kfsus = Kfs*us;
UF = Kff \ -((Kfs*us) - Ff)
yield respectively:
UF =
24.0742
35.4160
fval =
0
0
UF =
24.0742
35.4160
Hazem El Sankari
2018-11-21
Star Strider
2018-11-21
My pleasure.
If my Answer helped you solve your problem, please Accept it!
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