Returns the formula(s) for the different parts of a model (like fixed or random effects, zero-inflated component, ...).

find_formula(x, ...)



A fitted model.


Currently not used.


A list of formulas that describe the model. For simple models, only one list-element, conditional, is returned. For more complex models, the returned list may have following elements:

  • conditional, the "fixed effects" part from the model. One exception are DirichletRegModel models from DirichletReg, which has two or three components, depending on model.

  • random, the "random effects" part from the model (or the id for gee-models and similar)

  • zero_inflated, the "fixed effects" part from the zero-inflation component of the model

  • zero_inflated_random, the "random effects" part from the zero-inflation component of the model

  • dispersion, the dispersion formula

  • instruments, for fixed-effects regressions like ivreg, felm or plm, the instrumental variables

  • cluster, for fixed-effects regressions like felm, the cluster specification

  • correlation, for models with correlation-component like gls, the formula that describes the correlation structure

  • slopes, for fixed-effects individual-slope models like feis, the formula for the slope parameters

  • precision, for DirichletRegModel models from DirichletReg, when parametrization (i.e. model) is "alternative".


For models of class lme or gls the correlation-component is only returned, when it is explicitly defined as named argument (form), e.g. corAR1(form = ~1 | Mare)


data(mtcars) m <- lm(mpg ~ wt + cyl + vs, data = mtcars) find_formula(m)
#> $conditional #> mpg ~ wt + cyl + vs #> <environment: 0x0000000029bf04d0> #>