[R] Monotonic regression in R??

[Prof Brian D Ripley]

Here is a solution using C code:

library(MASS)
isoreg <- function(x, y)
{
    ord <- order(x)
    y <- y[ord]
    nd <- length(ord)
    Z <- .C("VR_mds_fn",
            as.double(y), yf=as.double(y), as.integer(nd),
            ssq = double(1), as.integer(order(ord)-1), as.double(x),
            as.integer(0), as.integer(0), g=double(0), as.integer(0),
            PACKAGE = "MASS")
    list(x = x[ord], y = y, fitted = Z$yf, RSS = Z$ssq)
}

I have not checked what happens it there are ties in the x's.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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