Re: How to use Needs inside While?

*To*: mathgroup at smc.vnet.net*Subject*: [mg6324] Re: [mg6302] How to use Needs inside While?*From*: Allan Hayes <hay at haystack.demon.co.uk>*Date*: Sat, 8 Mar 1997 23:26:47 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

sergio at scisun.sci.ccny.cuny.edu (Sergio Rojas) [mg6302] How to use Needs inside While? sends the problem copied below the line ************. Sergio: It looks like the problem arises because the symbols in an expression are created *before* evaluation. So, with Needs inside the loop, NonlinearFit is created as Global`NonlinearFit not Statistics`NonlinearFit. One possible way out might be to replace NonlinearFit in the body of the loop with Statistics`NonlinearFit. Allan Hayes hay at haystack.demon.co.uk http://www.haystack.demon.co.uk ******************************************************* Hello fellows, If I put the expression Needs["Statistics`NonlinearFit`"] inside a While loop, the function NonlinearFit does not work and Mathematica output the error: NonlinearFit::shdw: Warning: Symbol NonlinearFit appears in multiple contexts {Statistics`NonlinearFit`, Global`}; definitions in context Statistics`NonlinearFit` may shadow or be shadowed by other definitions. If the statement is outside the loop, no error is displayed and NonlinearFit works fine. How to use Needs["..."] inside any loop ? Example: Needs["Statistics`NonlinearFit`"];(* here it works *) answer = 0; While[ answer == 0, (* Needs["Statistics`NonlinearFit`"]; (* here it does not work *) Clear[a,b,c,d,abcd]; xmin = Input[" Enter xmin (try -4.)"]; xmax = Input[" Enter xmax (try 0.)"]; incr = Input[" Enter the increment (try 0.1)"]; data = Table[{x, 1.5*Exp[1.5*x] + 1.5*Sin[1.5*x]}, {x, xmin, xmax, incr}]; abcd = NonlinearFit[data, a*Exp[b*x] + c*Sin[d*x], x, {a,b,c,d}]; a = a /. abcd ; b = b /. abcd ; c = c /. abcd ; d = d /. abcd ; Print[" a= ", a," ; b= ",b," ; c= ",c," ; d= ",d]; answer = Input[" To try other interval, enter 0 and hit RETURN "]] Sergio E-mail: sergio at scisun.sci.ccny.cuny.edu