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Please note that the recommended version of Scilab is 6.0.2. This page might be outdated.

See the recommended documentation of this function

# fchamp

direction field of a 2D first order ODE

### Syntax

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.

### 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)

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