`lm`

is called if `mreg = "linear"`

. `glm`

is called with `family = binomial()`

if `mreg = "logistic"`

.

`fit_mreg(mreg, data, avar, mvar, cvar, emm_ac_mreg = NULL)`

## Arguments

- mreg
A character vector of length 1. Mediator regression type: `"linear"`

or `"logistic"`

.

- data
Data frame containing the following relevant variables.

- avar
A character vector of length 1. Treatment variable name.

- mvar
A character vector of length 1. Mediator variable name.

- cvar
A character vector of length > 0. Covariate names. Use `NULL`

if there is no covariate. However, this is a highly suspicious situation. Even if `avar`

is randomized, `mvar`

is not. Thus, there are usually some confounder(s) to account for the common cause structure (confounding) between `mvar`

and `yvar`

.

- emm_ac_mreg
A character vector of length > 0. Effect modifiers names. The covariate vector in treatment-covariate product term in the mediator model.

## Value

A regression object of class lm (linear) or glm (logistic)