direction field of a 2D first order ODE
fchamp(f, t, xr, yr, [arfact, rect, strf]) fchamp(f, t, xr, yr, <opt_args>)
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
.
the selected time.
two row vectors of size n1
and
n2
which define the grid on
which the direction field is computed.
This represents a sequence of statements
key1=value1, key2=value2
,...
where key1
, key2
,...
can be one of the following: arfact
,
rect
, strf
(see
below).
Optional arguments, see champ
.
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.
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") | ![]() | ![]() |