Dear R users -- I have a simple question that I cannot find the answers in the archive email: how to plot a multivariate function if I know the coefficients already? For instance, if I like to plot a 3D fig of Pi against X and Y with the function Pi = a0 + a1X + a2Y, where a0, a1 & a2 are known. Can "curve" do this? So far, I have only seen univariate case. Thank you. Yihsu Chen
Gavin Simpson
2008-Dec-10 11:35 UTC
[R] plot multivariate function with known coefficient.
On Tue, 2008-12-09 at 16:07 -0800, YIHSU CHEN wrote:> Dear R users -- > > I have a simple question that I cannot find the answers in the archive > email: how to plot a multivariate function if I know the coefficients > already? For instance, if I like to plot a 3D fig of Pi against X and > Y with the function Pi = a0 + a1X + a2Y, where a0, a1 & a2 are known. > Can "curve" do this? So far, I have only seen univariate case.Not sure about a "curve3D()" but you can do this yourself using expand.grid (to give combinations of X and Y you wish to evaluate Pi at) and then use the vectorised nature of R to compute Pi for the combinations given known coefficients. E.g.: X <- seq(1, 100, by = 5) Y <- seq(1, 100, by = 5) XY <- expand.grid(X = X, Y = Y) a0 <- 2 a1 <- 0.5 a2 <- -0.3 Pi <- with(XY, a0 + (a1 * X) + (a2 * Y)) Pi <- matrix(Pi, ncol = length(X), byrow = TRUE) persp(X, Y, Pi) HTH G> > Thank you. > > Yihsu Chen > > ______________________________________________ > R-help at 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.-- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Dr. Gavin Simpson [t] +44 (0)20 7679 0522 ECRC, UCL Geography, [f] +44 (0)20 7679 0565 Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ UK. WC1E 6BT. [w] http://www.freshwaters.org.uk %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 197 bytes Desc: This is a digitally signed message part URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20081210/ff554eac/attachment.bin>