Estimating a Statistical Model

The zelig function estimates a variety of statistical models. Use zelig output with setx and sim to compute quantities of interest, such as predicted probabilities, expected values, and first differences, along with the associated measures of uncertainty (standard errors and confidence intervals).

zelig(formula, model, data, ..., by = NULL, cite = TRUE)

Arguments

formula	a symbolic representation of the model to be estimated, in the form y \~\, x1 + x2, where y is the dependent variable and x1 and x2 are the explanatory variables, and y, x1, and x2 are contained in the same dataset. (You may include more than two explanatory variables, of course.) The + symbol means ``inclusion'' not ``addition.'' You may also include interaction terms and main effects in the form x1*x2 without computing them in prior steps; I(x1*x2) to include only the interaction term and exclude the main effects; and quadratic terms in the form I(x1^2).
model	the name of a statistical model to estimate. For a list of other supported models and their documentation see: http://docs.zeligproject.org/articles/.
data	the name of a data frame containing the variables referenced in the formula or a list of multiply imputed data frames each having the same variable names and row numbers (created by Amelia or to_zelig_mi).
...	additional arguments passed to zelig, relevant for the model to be estimated.
by	a factor variable contained in data. If supplied, zelig will subset the data frame based on the levels in the by variable, and estimate a model for each subset. This can save a considerable amount of effort. For example, to run the same model on all fifty states, you could use: z.out <- zelig(y ~ x1 + x2, data = mydata, model = 'ls', by = 'state') You may also use by to run models using MatchIt subclasses.
cite	If is set to 'TRUE' (default), the model citation will be printed to the console.

Value

Depending on the class of model selected, zelig will return an object with elements including coefficients, residuals, and formula which may be summarized using summary(z.out) or individually extracted using, for example, coef(z.out). See http://docs.zeligproject.org/articles/getters.html for a list of functions to extract model components. You can also extract whole fitted model objects using from_zelig_model.

Details

This documentation describes the zelig Zelig 4 compatibility wrapper function.

Additional parameters avaialable to many models include:

• weights: vector of weight values or a name of a variable in the dataset by which to weight the model. For more information see: http://docs.zeligproject.org/articles/weights.html.

• bootstrap: logical or numeric. If FALSE don't use bootstraps to robustly estimate uncertainty around model parameters due to sampling error. If an integer is supplied, the number of boostraps to run. For more information see: http://docs.zeligproject.org/articles/bootstraps.html.

See also

http://docs.zeligproject.org/articles/