Data used for the estimation about fixest HOT 3 CLOSED

library(fixest)

base = iris
names(base) = c("y", "x1", "x2", "x3", "species")
base$y[1] = NA
base$y[base$species == "versicolor"] = 0

(res = fepois(y ~ x1 + x2 | species, base))
#> NOTES: 1 observation removed because of NA values (Breakup: LHS: 1, RHS: 0, Fixed-effects: 0).
#>        1 fixed-effect (50 observations) removed because of only zero outcomes.
#> Poisson estimation, Dep. Var.: y
#> Observations: 99 
#> Fixed-effects: species: 2
#> Standard-errors: Clustered (species) 
#>    Estimate Std. Error z value   Pr(>|z|)    
#> x1 0.089710   0.045578  1.9683 4.9034e-02 *  
#> x2 0.124233   0.017720  7.0109 2.3700e-12 ***
#> ---
#> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#> Log-likelihood: -179.54   Adj. Pseudo-R2: 0.02014 
#>            BIC:  377.47     Squared Cor.: 0.90493

# Vector of observation IDs removed
head(res$obsRemoved)
#> [1]  1 51 52 53 54 55

# Fixed-effects removed because of only 0 outcomes
res$fixef_removed
#> $species
#> [1] "versicolor"

> base = iris
> names(base) = c("y", "x1", "x2", "x3", "species")
> 
> base$y[1] = NA
> base$x1[3] = NA
> base$x2[5] = NA
> base$species[15:17] = NA
> 
> est = feols(y ~ x1 + x2 | species, base)
#> NOTE: 6 observations removed because of NA values (Breakup: LHS: 1, RHS: 2, Fixed-effects: 3).
> 
> est$obsRemoved
#> [1]  1  3  5 15 16 17