In a symbolic expression, how can I extract all terms that have a common specific variable?

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Kevin Bachovchin 2013-3-21

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采纳的回答： Azzi Abdelmalek

Hello,

In a symbolic expression, is there a way to extract all terms that have a common specific variables? For example, if I have the symoblic function

dxdt = f(a,b,c)*x1+f(a,b,c)*x2+f(a,b,c)*x1+f(a,b,c)*x3+...

Is there a way to extract all terms in dxdt that have x1 in them? I'm looking to try to put my expression dxdt in standard state space form. (My symbolic function can be very lengthy, so using the simplify function is not necessarily grouping all the x1 terms together.)

Thank you, Kevin

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Azzi Abdelmalek 2013-3-21

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编辑：Azzi Abdelmalek 2013-3-21

在 MATLAB Online 中打开

Use collect function

collect(dxdt,x1)

and coeffs function

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Kevin Bachovchin 2013-3-21

Thanks, that works.

Kevin Bachovchin 2013-3-21

Just using coeffs by itself seems to work the same also.

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