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Subject: Re: nonlinear constraint help
Date: Fri, 18 Sep 2009 15:12:02 +0000 (UTC)
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"Simone " <simonematool@gmail.com> wrote in message <h8ufpv$2iq$1@fred.mathworks.com>...
> Hello to all,
> 
> I have two maybe very dumb questions but I cannot get my head around these: I have a problem subject to 18 linear constraints and 1 nonlinear constraint. In this last one appear in part variables present also in the linear ones and other variables.
>  Questions: 
> 1. from the nonlinear constraint to recall the variables present in the linear constraints, I'm calling them with x(position), given the example here http://www.mathworks.com/access/helpdesk/help/toolbox/optim/index.html?/access/helpdesk/help/toolbox/optim/ug/brhkghv-7.html&http://www.mathworks.com/matlabcentral/newsreader/view_thread/256555 is this correct? 
====================

Yes.


> 
> 2. the second question is if I can add more variables to be solved for in the nonlinear constraint, but these would be only in this constraint
==============

Yes.

 (they are multiplied by the other variables present also in the linear constraints so they should be identified, isn't it?). I have seen the documentation on how to pass parameters in the nonlinear constraints but not variables, is this possible?
================

If your variables decompose as [x,y] where x and y are vectors, then neither your objective function f(x,y) nor your constraints Ci(x,y) have to have an explicit dependence on both x and y, even if they both take x and y as input arguments.


However, if f(x,y) is independent of y, i.e. can theoretically be written f(x), that gives the algorithm more freedom in finding a y that satisfies Ci(x,y)>=0. If it's important to distinguish between more than one possible solution for y, you must of course add more constraints....