How can I equate coefficients of the like powers from rhs and lhs in an equation to obtain a system of ODEs?

Hi everyone, I have a long equation EQ12.

Is there a way of getting this from Symbolic Math Toolbox? I have tried to play around with coeffs but no luck. Thank you in advance for any help. Cheers.

[Walter Roberson]

See coeffs() . You might want to use the 'all' option to make it easier to match up.

But have you considered using odeFunction ? I recommend following the workflow given in the first example there.

Answer 1

[Devineni Aslesha]

Hi Silvia,

You can use the coeffs function to equate like powers of t and obtain the corresponding ODEs.

eqn = lhs(EQ12)-rhs(EQ12) == 0
c = coeffs(eqn,t)

Here, c is a 1*6 symbol in which c(1,1) = "- diff(F[0](z), z, z) + diff(F[0](z), z) + F[0](z)^2" which is the coefficient of t. Similarly, you have coefficients for other powers of t. Now, you can use the equation c(1,1) == 0 for further calculations.

For more information, refer the following links

https://www.mathworks.com/help/symbolic/coeffs.html

[Silvia Ceccacci]

Hi Aslesha,

I have tried wht you suggested, but it doesn't seem to tidy up the equations.

EQ12 = collect(EQ11,t);
EQ13 = lhs(EQ12)-rhs(EQ12) == 0;
coef = coeffs(EQ13,t);
coef_t = coef(1,1) == 0

So basically it has put all the term on the lhs but not given me the system of ODEs by equating the powers of t. Thank you for your help. Silvia