ercomp {plm} | R Documentation

## Estimation of the error components

### Description

This function enables the estimation of the variance components of a panel model.

### Usage

    ercomp(object, ...)
    ## S3 method for class 'formula'
    ercomp(object, data,
                             effect = c("individual", "time","twoways", "nested"),
                             method = NULL, models = NULL,
                             dfcor = NULL, index = NULL, ...)
    ## S3 method for class 'plm'
    ercomp(object, ...)
    ## S3 method for class 'ercomp'
    print(x, digits= max(3, getOption("digits") - 3), ...)

### Arguments

`object` | a `formula` or a `plm` object,
`data` | a `data.frame`,
`effect` | the effects introduced in the model, see `plm` for details,
`method` | method of estimation for the variance components, see `plm` for details,
`models` | the models used to estimate the variance components (an alternative to the previous argument),
`dfcor` | a numeric vector of length 2 indicating which degree of freedom should be used,
`index` | the indexes,
`x` | an `ercomp` object,
`digits` | digits,
`...` | further arguments.

### Value

An object of class `"ercomp"`: a list containing

- `sigma2` a named numeric with estimates of the variance components,

- `theta` contains the parameter(s) used for the transformation of the variables: For a one-way model, a numeric corresponding to the selected effect (individual or time); for a two-ways model a list of length 3 with the parameters. In case of a balanced model, the numeric has length 1 while for an unbalanced model, the numerics' length equal the number of observations.

### Author(s)

Yves Croissant

### References

Amemiya, T. (1971) The estimation of the variances in a variance–components model, International Economic Review, 12(1), pp. 1–13.

Nerlove, M. (1971) Further evidence on the estimation of dynamic economic relations from a time series of cross sections, Econometrica, 39(2), pp. 359–382.

Swamy, P.A.V.B. and Arora, S.S. (1972) The exact finite sample properties of the estimators of coefficients in the error components regression models, Econometrica, 40(2), pp. 261–275.

Wallace, T.D. and Hussain, A. (1969) The use of error components models in combining cross section with time series data, Econometrica, 37(1), pp. 55–72.

### See Also

`plm` where the estimates of the variance components are used if a random effects model is estimated

### Examples

    data("Produc", package = "plm")
    # an example of the formula method
    ercomp(log(gsp) ~ log(pcap) + log(pc) + log(emp) + unemp, data = Produc,
           method = "walhus", effect = "time")
    # same with the plm method
    z <- plm(log(gsp) ~ log(pcap) + log(pc) + log(emp) + unemp,
             data = Produc, random.method = "walhus",
             effect = "time", model = "random")
    ercomp(z)
    # a two-ways model
    ercomp(log(gsp) ~ log(pcap) + log(pc) + log(emp) + unemp, data = Produc,
           method = "amemiya", effect = "twoways")

[Package plm version 1.6-6 Index]