Robust Line Fitting

line

Robust Line Fitting

Description

Fits a tukey line.

Usage

line(x, y = NULL)
## S3 method for class 'tukeyline':
print(x, digits = max(3L, getOption("digits") - 3L), ...)

Arguments

x	the x coordinates of points. If y is missing, x should be an object implicitly containing x-y data: a 2-column matrix, a list with components named x and y, a complex vector, a ts object, or a numeric vector. See xy.coords for more details. For the print method, x is an object of class "tukeyline", typically producted by line.
y	the y coordinates of points.
digits	the maximum number of (significant) digits to use for coefficients of tukey line.
...	other optional arguments passed to generic function.

Details

line fits a line through the points using a simple robust algorithm that Tukey described in reference Exploratory Data Analysis. The slope is the slope of the line passing through the x and y medians of the left and right thirds of the data; the intercept is chosen so that the median residual is 0.

Value

line returns a list of class "tukeyline" with following components:

call	system call of this function.
coefficients	the coefficients, intercept then slope, of the fitted line.
residuals	the actual y values minus the fitted values.
fitted.values	the y values on the fitted line at the observed x values.

print.tukeyline, like other print methods, returns its x argument invisibly.

References

Tukey, J. W. 1977. Exploratory Data Analysis. Reading, MA: Addison-Wesley Pub.