FindMinimum

*To*: mathgroup at smc.vnet.net*Subject*: [mg15823] FindMinimum*From*: "Hossein Kazemi" <kazemi at javanet.com>*Date*: Fri, 12 Feb 1999 18:39:44 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

I have an expression that involves the Sign[] function. For example, consider f=Sign[4.35x-13.57y +(1-x^2-y^2)]-Sign[2.49x-11.18y+(1-x^2-y^2)]+... I need to find the minimum of this function. Since the symbolic derivatives with respect to x and y do not exist, I have to use FindMinimum[f,{x,{x0,x1}},{y,{y0,y1}}] But this does not restrict Mathematica not look outside (-1,1) range for solutions, where (1 - x^2 - y^2) will not be real. Is there anyway to find the minimum of a function when symbolic derivatives of the function do not exist and values outside a range should not be used. Thank you. kazemi at som.umass.edi