Re: vpasolve to find all real roots for multiple nonlinear equations and multiple variables

[Colin Macdonald]

On 30/05/16 08:45, sam kjm wrote:
> equations = [ss_prot1, ss_prot2];

I pasted in your code and got:

>> equations = [ss_prot1, ss_prot2];
error: 'ss_prot2' undefined near line 1 column 23

> Is there probably another way to vpasolve? I tried fsolve before but it
> needs initial values so it gives me only 1 answer for prot1 and 1 answer for
> prot2s for a particular start value for prot1 and prot2s

You said "main aim is to find all real roots for 2 nonlinear equations".
 This is hard problem in general (because nonlinear).
Algorithm-wise, `vpasolve` is going to pretty much do what `fsolve`
does.  It will also need a initial guess (I think it makes one up---like
zero---if you don't specify it).  Roughly speaking, `vpasolve` is
intended for use when you need more than 16 digits of precision from
`fsolve`.

address@hidden/solve` in some cases can solve nonlinear equations symbolically
(finding all solutions).  I would suggest trying that first.  But drop
the `vpa` stuff.  And perhaps look at the warnings you're getting from
converting all your constants to symbolic.


best,
Colin