> > Suppose there are 4 variables > d is a function of a , b and c > I want to know how a, b and c change will make d change > It will be straightforward to see it if we can graph the d surface > > if d is only a function of a and b, I can use 'persp' to see the surface of > d. I can easily see at what values of a and b, d will get the maxium or > minium or multiple modes, etc > > But for 4 dimention graph, is there a way to show the surface of d > Will use color help > > Thanks a lot
Not sure what your data looks like, but you might also consider looking at a 2 dimensional version. See ?coplot for example: coplot(lat ~ long | depth * mag, data = quakes) Or you can make 2 or 3-dimensional plots using the lattice package conditioning on some of the variables - e.g. d ~ a | b * c, etc. If a, b, and c are "continuous", you can use equal.count. Here is an uninteresting example, considering a, b, and c as points along a grid: a <- b <- c <- seq(1:10) dat <- data.frame(expand.grid(a, b, c)) names(dat) <- letters[1:3] dat$d <- with(dat, -(a-5)^2 - (b-5)^2 - (c-5)^2) library(lattice) # 2-d: xyplot(d ~ a | equal.count(b)*equal.count(c), data=dat, type="l") # etc. # 3-d: contourplot(d ~ a * b | equal.count(c), data=dat) wireframe(d ~ a * b | equal.count(c), data=dat) ______________________________________________ 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.