Fixed effect counts in modelsummary

I have a modelsummary of three fixed effects regressions like so:

remotes::install_github("lrberge/fixest")
remotes::install_github("vincentarelbundock/modelsummary")

library(fixest)
library(modelsummary)

mod1 <- feols(mpg ~ hp | cyl, data = mtcars)
mod2 <- feols(mpg ~ wt | cyl, data = mtcars)
mod3 <- feols(mpg ~ drat | cyl, data = mtcars)

modelsummary(list(mod1, mod2, mod3), output = "markdown")

Instead of having the table show merely whether certain fixed effects were present, is it possible to show the number of fixed effects that were estimated instead?

The raw models do contain this information:

> mod1
OLS estimation, Dep. Var.: mpg
Observations: 32 
Fixed-effects: cyl: 3
Standard-errors: Clustered (cyl) 
    Estimate Std. Error  t value Pr(>|t|) 
hp -0.024039   0.015344 -1.56664  0.25771 
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
RMSE: 2.94304     Adj. R2: 0.727485
                Within R2: 0.07998 

Yes, you’ll need to define a glance_custom.fixest() method. See this section of the docs for detailed instructions and many examples:

https://vincentarelbundock.github.io/modelsummary/articles/modelsummary.html#customizing-existing-models-part-i

And here’s an example with fixest:

library(fixest)
library(tibble)
library(modelsummary)

models <- list(
    feols(mpg ~ hp | cyl, data = mtcars),
    feols(mpg ~ hp | am, data = mtcars),
    feols(mpg ~ hp | cyl + am, data = mtcars)
)

glance_custom.fixest <- function(x, ...) {
    tibble::tibble(`# FE` = paste(x$fixef_sizes, collapse = " + "))
}

modelsummary(models, gof_map = c("nobs", "# FE"))