This dialog is used to specify a generalized linear model to be fit by the
`glm`

function.

The left model-formula box specifies the response variable to be used in the model; it
may be a variable name or an expression evaluating to the response variable, such as
`working == "Fulltime"`

.

The right model-formula box specifies the right-hand (i.e., predictor) side of the model.
See `glm`

for details.

You can type directly in the model formula boxes. Alternatively, double-clicking the left mouse
button on a variable in the variable-list transfers it to the left-hand side of the model (if
it is empty or selected) or to the right-hand side.
Factors are indicated in the variable list; all other variables are numeric.
You can also enter operators and parentheses using the buttons
above the formula. If you select several variables in the variable-list box, clicking on the
`+`

, `*`

, or `:`

button will enter them into the model formula.

Double-click the left mouse button to select a family in the "Family" box and the corresponding
permissible link functions appear in the "Link function" box to the right. Initially, the
canonical link for the family is selected. See `family`

for details.

Specifying a subset expression allows you to fit the model to a subset of observations
in the active data set. For example, assuming that `gender`

is a variable in the
active data set, entering `gender == "Male"`

would restrict the model to males.

The weights box allows you to select a variable specifying prior weights from the drop-down list. Weights giving numbers of trials may be used, for example, to fit a binomial GLM; in this case, the response variable should give the proportion of "successes" for each binomial observation. Click in the weights combo box to see a list of numeric variables in the current data set; type a letter in the box to move the selection cursor to the next variable beginning with that letter.

If the active model is a generalized linear model, and the active data set has not changed, then the initial values of the left-hand-side, right-hand-side, family, link, weights, and subset fields are retained from the active model.