summary.rlm {MASS} | R Documentation

## Summary Method for Robust Linear Models

### Description

`summary` method for objects of class `"rlm"`

### Usage

    summary(object, method=c("XtX", "XtWX"), correlation=TRUE, ...)

### Arguments

`object` | the fitted model. This is assumed to be the result of some fit that produces an object inheriting from the class `rlm`, in the sense that the components returned by the `rlm` function will be available.
`method` | Should the weighted (by the IWLS weights) or unweighted cross-products matrix be used?
`correlation` | logical. Should correlations be computed (and printed)?

### Details

This function is a method for the generic function `summary()` for class `"rlm"`. It can be invoked by calling `summary(x)` for an object `x` of the appropriate class, or directly by calling `summary.rlm(x)` regardless of the class of the object.

### Value

If printing takes place, only a null value is returned. Otherwise, a list is returned with the following components. Printing always takes place if this function is invoked automatically as a method for the `summary` function.

`correlation` | The computed correlation coefficient matrix for the coefficients in the model.
`cov.unscaled` | The unscaled covariance matrix; i.e, a matrix such that multiplying it by an estimate of the error variance produces an estimated covariance matrix for the coefficients.
`sigma` | The scale estimate.
`df` | The number of degrees of freedom for the model and for residuals.
`coefficients` | A matrix with three columns, containing the coefficients, their standard errors and the corresponding t statistic.
`terms` | The terms object used in fitting this model.

### See Also

`summary`

### Examples

    data(phones)
    summary(rlm(calls ~ year, data=phones, maxit=50))

    Call:
    rlm(formula = calls ~ year, data = phones, maxit = 50)

    Residuals:
       Min     1Q Median     3Q    Max
    -18.31  -5.95  -1.68  26.46 173.77

    Coefficients:
                Value    Std. Error t value
    (Intercept) -102.622   26.553   -3.86
    year           2.041    0.429    4.76

    Residual standard error: 9.03 on 22 degrees of freedom

    Correlation of Coefficients:
    [1] -0.994