psiFunc {robustbase} | R Documentation

## Constructor for Objects "Psi Function" Class

### Description

`psiFunc(..)` is a convenience interface to `new("psi_func",..)`, i.e. for constructing objects of class `"psi_func"`.

### Usage

    psiFunc(rho, psi, wgt, Dpsi,Dwgt, Erho = NULL, Epsi2 = NULL, EDpsi = NULL, name, ...)

    huberPsi
    hampelPsi

### Arguments

`rho, psi, wgt, Dpsi, Dwgt` | each a `function` of `x` and tuning parameters typically. Specification of Dwgt is optional.
`Erho, Epsi2, EDpsi` | see `psi_func`, and note that these may change in the future.
`name` | Name of psi-function used for printing.
`...` | potential further arguments for specifying tuning parameter names and defaults.

### Author(s)

Martin Maechler

### See Also

The description of class `psi_func`.

### Examples

    plot(huberPsi) # => shows "all" {as an object with a smart plot() method}

    ## classical (Gaussian / "least-squares") psi {trivial}:
    F1 <- function(x, .) rep.int(1, length(x))
    FF <- function(.) rep.int(1, length(.))
    cPsi <- psiFunc(rho = function(x,.) x^2 / 2, psi = function(x, .) x,
                    wgt = F1, Dpsi = F1,
                    Erho = function(.) rep.int(1/2, length(.)),
                    Epsi2 = FF, EDpsi = FF, name = "classic", . = Inf)
    show(cPsi)
    plot(cPsi)
    ## is the same as the limit of Huber's:
    plot(chgDefaults(huberPsi, k = Inf))

    ## Hampel's psi and rho:
    H.38 <- chgDefaults(hampelPsi, k = c(1.5, 3.5, 8))
    k. <- H.38@xtras$tuningP$k ; k.. <- as.vector(outer(c(-1,1), k.))
    c.t <- adjustcolor("skyblue3", .8)
    .ax.k <- function(side) { abline(h=0, v=0, lty=2)
      axis(side, at = k.., labels=formatC(k..), pos=0, col=c.t, col.axis=c.t) }
    op <- par(mfrow=c(2,1), mgp = c(1.5, .6, 0), mar = .6+c(2,2,1,.5))
    curve(H.38@psi(x), -10, 10, col=2, lwd=2, n=512)
    lines(k.., H.38@psi(k..), type = "h", lty=3, col=c.t); .ax.k(1)
    curve(H.38@rho(x), -10, 10, col=2, lwd=2, n=512); abline(h=0, v=0, lty=2)
    lines(k.., H.38@rho(k..), type = "h", lty=3, col=c.t); .ax.k(1)
    title(expression("Hampel's " ~~~ psi(x) ~~ "and" ~~ rho(x) ~~~ " functions"))
    par(op)

    ## Not the same, but similar, directly using the plot() method:
    plot(H.38)

[Package robustbase version 0.93-4 Index]