R: Scatter Plot with Smooth Curve Fitted by Loess

scatter.smooth {stats} | R Documentation

## Scatter Plot with Smooth Curve Fitted by Loess

### Description

Plot and add a smooth curve computed by `loess` to a scatter plot.

### Usage

    scatter.smooth(x, y = NULL, span = 2/3, degree = 1,
        family = c("symmetric", "gaussian"),
        xlab = NULL, ylab = NULL,
        ylim = range(y, prediction$y, na.rm = TRUE),
        evaluation = 50, ...)

    loess.smooth(x, y, span = 2/3, degree = 1,
        family = c("symmetric", "gaussian"), evaluation = 50, ...)

### Arguments

`x,y` | the `x` and `y` arguments provide the x and y coordinates for the plot. Any reasonable way of defining the coordinates is acceptable. See the function `xy.coords` for details.
`span` | smoothness parameter for `loess`.
`degree` | degree of local polynomial used.
`family` | if `"gaussian"` fitting is by least-squares, and if `family="symmetric"` a re-descending M estimator is used.
`xlab` | label for x axis.
`ylab` | label for y axis.
`ylim` | the y limits of the plot.
`evaluation` | number of points at which to evaluate the smooth curve.
`...` | graphical parameters.

### Details

`loess.smooth` is an auxiliary function which evaluates the `loess` smooth at `evaluation` equally spaced points covering the range of `x`.

### Value

For `scatter.smooth`, none.
For `loess.smooth`, a list with two components, `x` (the grid of evaluation points) and `y` (the smoothed values at the grid points).

### See Also

`loess`

### Examples

    require(graphics)

    with(cars, scatter.smooth(speed, dist))

[Package stats version 2.8.1 Index]