On 13-12-05 7:02 PM, Jun Shen wrote:
Thanks again, Duncan. Please allow me to ask one more question. Is it possible to generate a contour plot overlaying with the plot3d() plot?
Yes, the contourLines function from grDevices can calculate the lines, then you can use rgl::lines3d to draw them.
Duncan Murdoch
Jun On Thu, Dec 5, 2013 at 11:08 AM, Duncan Murdoch <murdoch.dun...@gmail.com <mailto:murdoch.dun...@gmail.com>> wrote: On 05/12/2013 10:33 AM, Jun Shen wrote: Hi Federico/Duncan/David/Bert, Thank you for your thoughtful comments and it's a great learning experience. I can see the critical point here is to find a right function to make the prediction. So I was thinking to start with "loess". However the predict.loess gave me an error as follows Error in `$<-.data.frame`(`*tmp*`, "z", value = c(0.417071766265867, 0.433916401753023, : replacement has 20 rows, data has 400 Here is the code I tried. Thank you for your help again! Jun ==============================__======= x<-runif(20) y<-runif(20) z<-runif(20) library(rgl) plot3d(x,y,z) loess(z~x+y,control=loess.__control(surface='direct'),__span=.5,degree=2)->fit.loess xnew <- seq(min(x), max(x), len=20) ynew <- seq(min(y), max(y), len=20) df <- expand.grid(x = xnew, y = ynew) df$z<-predict(fit.loess,__newdata=df) After the error, use traceback() to find which function called `$<-.data.frame`. It shows that it was your final assignment df$z<-predict(fit.loess,__newdata=df) which causes the error, because the predict function returns a matrix. So you can get the plot using surface3d(xnew, ynew, predict(fit.loess,newdata=df), col="gray") You may want aspect3d(1,1,1) afterwards; loess isn't so good at extrapolation. Or you may want to set predictions to NA outside the convex hull of your data. (I'm not sure which function is easiest to calculate that, but here's one way: hullx <- x[chull(x,y)] hully <- y[chull(x,y)] keep <- sp::point.in.polygon(df$x, df$y, hullx, hully) znew <- predict(fit.loess,newdata=df) znew[!keep] <- NA plot3d(x,y,z) surface3d(xnew, ynew, znew, col="gray") aspect3d(1,1,1)
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