Solving equation with symbolic vector variable
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I want to solve an equation of the form: V/(A-V)=B where A and B are known vectors and V is the symbolic vector variable I want to solve for. I created V by >>V=sym('V',[n 1]); and solved the equation by using 'solve' but in the output I get only the 'names' of the elements - V1, V2, V3, ... How do I get the values of V1, V2,...? Any help is much appreciated.
2 个评论
Walter Roberson
2013-11-16
Is the division to be matrix division, or element-by-element?
Rinu
2013-11-16
采纳的回答
Walter Roberson
2013-11-16
V = B .* A ./ (B + 1);
15 个评论
Rinu
2013-11-17
Rinu
2013-11-17
Walter Roberson
2013-11-17
So V/(A-V)=B is not really the form you are using? Or is it just "expensive" to calculate A and B ?
Rinu
2013-11-17
Walter Roberson
2013-11-17
Could you show your solve() command ?
Rinu
2013-11-17
Rinu
2013-11-17
Walter Roberson
2013-11-17
Which of those are intended to be numeric and which are intended to involve symbols? Are there any symbols present other that the V ? Are you assigning the output to anything?
Rinu
2013-11-17
Walter Roberson
2013-11-17
Kgasa = ((-Kwsat .* poro + Kw - Kg) .* Kq.^2 + Kwsat .* ((Kw + Kg) .* poro - Kw + Kg) .* Kq - Kwsat .* poro .* Kg .* Kw) ./ (-poro .* Kq.^2 + ((Kw + Kg) .* poro + Kw - Kg) * Kq + (Kg - Kw) .* Kwsat - poro .* Kg .* Kw)
Rinu
2013-11-17
Walter Roberson
2013-11-17
I simply used a symbolic package. The hard work was in editing the text to space it nicely and to add all of the "." in appropriate places ;-)
Alexander Kharlan
2016-5-6
Well, got the same problem, only I cannot avoid using symbolic variables. And here on top of google search quiery we have an 'accepted' answer that DOESN'T ANSWER THE GODDAMN QUESTION. Shame on your face. If you are content with people doing your job for you, however not connected with the question you've asked, would you please go to some other forum.
Walter Roberson
2016-5-7
Alexander Kharlan:
V = B .* A ./ (B + 1)
is the solution to the question originally presented. It turned out that question originally presented was not the real question, and the real question was solved to the user's satisfaction.
The more general question of how to solve a symbolic vector equation depends upon the release you are using . In current releases, you just use solve() on the vector equation. In slightly older releases, you use num2cell() to break the vector up into a cell array, and then you use cell array expansion to push the elements as separate parameters to solve(). For example,
mveq = num2cell(myVectorOfEquations);
mvvar = num2cell(VariablesToSolveFor);
solve(mveq{:}, mvvar{:})
Walter Roberson
2016-5-7
"If you are content with people doing your job for you"
Answering questions here is not my job. As far as I know, the only people who are paid to answer questions here are the Mathworks staff who work on the Answers forum software itself. Everyone else who answers questions here (including the other people who happen to work for Mathworks) does so as a volunteer. I do not work for Mathworks; I have never worked for Mathworks.
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