fchamp - direction field of a 2D first order ODE

Calling Sequence

fchamp(f,t,xr,yr,[arfact,rect,strf])

fchamp(f,t,xr,yr,<opt_args>)

Parameters

• f : An external (function or character string) or a list which describes the ODE.
  • - It can be a function name f , where f is supposed to be a function of type y=f(t,xy [p1,..pn]) . f returns a column vector of size 2, y , which gives the value of the direction field f at point xy=[x,y] and at time t .
  • - It can also be an object of type list, list(f,P1,..Pn) where f is a function of type y=f(t,xy,p1,..pn) and Pi gives the value of the parameter pi .
• t : The selected time.
• xr,yr : Two row vectors of size n1 and n2 which define the grid on which the direction field is computed.
• <opt_args> : This represents a sequence of statements key1=value1,key2=value2 , ... where key1 , key2,... can be one of the following: arfact, rect, strf (see below).
• arfact,rect,strf : Optional arguments, see champ .

Description

fchamp is used to draw the direction field of a 2D first order ODE defined by the external function f . Note that if the ODE is autonomous, argument t is useless, but it must be given.

Enter the command fchamp() to see a demo.

Examples

deff("[xdot] = derpol(t,x)",..
        ["xd1 = x(2)";..
         "xd2 = -x(1) + (1 - x(1)**2)*x(2)";..
         "xdot = [ xd1 ; xd2 ]"])
xf= -1:0.1:1;
yf= -1:0.1:1;
fchamp(derpol,0,xf,yf)
clf()
fchamp(derpol,0,xf,yf,1,[-2,-2,2,2],"011")
 
  

See Also

champ ,   champ1 ,  

Author

J.Ph.C.