A predefined panel function that can be used to add a LOESS smooth based on the provided data.
panel.loess(x, y, span = 2/3, degree = 1,
            family = c("symmetric", "gaussian"),
            evaluation = 50,
            lwd, lty, col, col.line, type,
            horizontal = FALSE,
            …, identifier = "loess")Variables defining the data to be used.
Graphical parameters for the added
    line.  col.line overrides col.
Ignored.  The argument is present only to make sure that
    an explicitly specified type argument (perhaps meant for
    another function) does not affect the display.
Arguments to
    loess.smooth, for which panel.loess is
    essentially a wrapper.
A logical flag controlling which variable is to be treated as the
    predictor (by default x) and which as the response (by
    default y).  If TRUE, the plot is ‘transposed’
    in the sense that y becomes the predictor and x the
    response.  (The name ‘horizontal’ may seem an odd choice for
    this argument, and originates from similar usage in
    bwplot).
Extra arguments, passed on to
    panel.lines.
A character string that is prepended to the names of grobs that are created by this panel function.
The object returned by loess.smooth.