Jong-Hoon Kim wrote:
> Dear useRs,
>
> I am trying to draw direction fields for some differential equations.
> So for I couldn't find much information on that. Could anybody give
> me a hint how to draw a direction field using R?
>
Hi Jong-Hoon,
Here's a start on a function.
direction.field<-function(dydx,xlim=c(-1,1),ylim=c(-1,1),
nxarrows=20,nyarrows=20,length=NA) {
xinc<-diff(xlim)/(nxarrows*2)
yinc<-diff(ylim)/(nyarrows*2)
if(is.na(length)) length<-par("pin")[1]/100
plot(0,xlim=xlim,ylim=ylim,type="n")
for(x in seq(xlim[1]+xinc,xlim[2]-xinc,length=nxarrows)) {
for(y in seq(ylim[1]+yinc,ylim[2]-yinc,length=nyarrows)) {
stan<-atan(eval(parse(text=dydx)))
arrows(x-xinc*cos(stan),y-yinc*sin(stan),
x+xinc*cos(stan),y+yinc*sin(stan),
length=length)
}
}
}
direction.field("0*x+1*y")
Jim
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
