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>)

Arguments

: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.

Sample

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)

`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;
`clf`_()
fchamp(derpol,0,xf,yf,1,[-2,-2,2,2],"011")

See Also

• champ 2D vector field plot
• champ1 2D vector field plot with colored arrows