Symbolic Math expression simplification
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Hello,
I am trying to simplify a symbolic expression, in terms of others,for example:
syms w L C;
Z = 1j*w*L + 1/(1j*w*C)
Ok, the result is (-w^2LC + 1)/(1jwC)
The question is, for example, if I want to simplify the result so that Matlab substitutes -w^2LC+1 for a variable like 'RF1', what should I do?
The simulation I am running outputs several (more than 100) combination from a complex ckt topology, many or all the combinations results could be simplified to Freq1, IntrisicImpedance, etc.
All the Best.
Ronaldo
采纳的回答
Walter Roberson
2016-4-20
1 个投票
6 个评论
Ronaldo Junior
2016-4-20
Ronaldo Junior
2016-4-20
Ronaldo Junior
2016-4-21
Walter Roberson
2016-4-21
Any time you use a symbolic variable in an expression, it is evaluated. If it evaluates to itself, then that meaning of it is "captured"; if it evaluates to a previously assigned expression then the expression is substituted including the "capturedness" of any names it might have included. In other words if you assign to a symbolic variable after you have used it in an expression, then the changed meaning only applies to its use in new expressions after that point.
syms a b c
c = a + b %"captures" the association of "a" with the symbol "a"
a = 7; %_new_ references to "a" will use 7
c %is still a + b not 7 + b
subs(c,sym('a'), a)
%the numeric a of 7 will be dropped in, making it the same as
subs(c, sym('a'), 7)
Then the symbol "a" will be found within c and the numeric substitution will be done
Ronaldo Junior
2016-4-21
Walter Roberson
2016-4-21
I am not sure but I think you might be asking about how to find common sub-expressions. That is a bit tricky because the symbolic engine is allowed to reorder expressions. You can work at it using op(), which does not have an interface at the MATLAB level.
Often the easiest approach is to take something like A*B*C and group it as G by using
subs(expression, A, G/(B*C))
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