# [R] help with bivariate density plot question

Spencer Graves spencer.graves at pdf.com
Sat Jul 12 17:17:48 CEST 2003

```Did you look at "?contour"?  The "contour" command has a "levels"
argument.  To translate op into percentage, you could produce an
empirical CDF of op\$zden.

hope this helps.  spencer graves

liping wrote:
> Dear R users:
>
> I have a dataset with two variables (>20000 observations, two samples from same subject) and I used "kernSur" from library(Genkern) to
> get a estimated bivariate density and corresponding plots as follows:
>
> new.data.normal<-data.normal[!is.na(data.normal[,2]),]
> x<-new.data.normal[,2]
> y<-new.data.normal[,3]
>
> op <- KernSur(x,y, xgridsize=50, ygridsize=50, correlation=0.4968023,
>               xbandwidth=1, ybandwidth=1)
>
> #3D density plot
> persp(op\$xvals, op\$yvals, op\$zden,
>         theta=30,phi=10,expand=0.5,ltheta=120,
>         xlab="TECH3661.A",ylab="TECH3661.B",zlab="Prob",col="pink",
>       , main="3D DENSITY PLOT-TECH3661 ", sub=" TECH3661.A AND TECH3661.B",
>         box = T, axes = TRUE,ticktype = "detailed", )
>
> #countour plot
> image(op\$xvals, op\$yvals, op\$zden, col=terrain.colors(100), axes=TRUE,xlab="TECH3661.A",ylab="TECH3661.B")
> points(x,y,pch="*")
>
> Now after above step, how can I use 'contour' or other commands to draw ellipse curves over above plots indicating "including about 68% data", "including about 84% data", etc. similar to the (-std,std), (-2*std,2*std),(-3*std, 3*std) intervals for univariate variable.
>
> any suggestin will be appreciated.
>
> liping
>
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```