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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution. The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
function []=fchamp(macr_f,fch_t,fch_xr,fch_yr,arfact,rect,strf)
// Draw vector field in R^2,
// Vector field defined by:
// y=f(x,t,[u]), for compatibility with ode function
// f : vector field. CAn be either :
// a function y=f(t,x,[u])
// a list such as list(f1,u1) with f1 a function
// y=f1(t,x,u) and u1=current value of u
// t : instants vector
// xr,yr: two vectors defining the gridding
// arfact : optional arg to control size of arrow heads,
// strf : string ( same as plot2d )
//Example : enter fchamp()
//!
[lhs,rhs]=argn(0)
if rhs <= 0 then // demo
deff("[xdot] = derpol(t,x)",["xd1 = x(2)"; ..
"xd2 = -x(1) + (1 - x(1)**2)*x(2)"; ..
"xdot = [ xd1 ; xd2 ]"]);
fchamp(derpol,0,-1:0.1:1,-1:0.1:1,1);
return
end
if rhs <= 1,fch_t=0;end
if rhs <= 2,fch_xr=-1:0.1:1;end
if rhs <= 3,fch_yr=-1:0.1:1;end
opts=[]
if exists("arfact","local")==1 then opts=[opts,"arfact=arfact"],end
if exists("rect","local")==1 then opts=[opts,"rect=rect"],end
if exists("strf","local")==1 then opts=[opts,"strf=strf"],end
if type(macr_f) <> 15,
if type(macr_f)==11 then comp(macr_f),end;
deff("[yy]=mmm(x1,x2)",["xx=macr_f(fch_t,[x1;x2])";"yy=xx(1)+%i*xx(2);"]);
else
mmm1=macr_f(1)
if type(mmm1)==11 then comp(mmm1),end;
deff("[yy]=mmm(x1,x2)",["xx=mmm1(fch_t,[x1;x2],macr_f(2));";
"yy=xx(1)+%i*xx(2);"]);
end
fch_v=feval(fch_xr,fch_yr,mmm);
execstr("champ(fch_xr,fch_yr,real(fch_v),imag(fch_v),"+strcat(opts,",")+")")
endfunction
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