fchamp

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)
xbasc()
fchamp(derpol,0,xf,yf,1,[-2,-2,2,2],"011")

Author

J.Ph.C.