Add tidiers for margins and mfx objects #700
Description
It would be great to have tidy methods for objects from the margins and mfx packages.
Among other things, this would go a long way towards improving the table support for generalized linear models like logit and probit regressions, where you often want to report actual marginal effects rather than the naive coefficient values. (I'm thinking of the fact that modern table-exporting packages like huxtable and gtsummary rely on broom::tidy() as a first step.) AFAIK, there is currently no fully automated way to produce, say, a LaTeX table of marginal effects from a logistic regression in R.
A potential point of convenience here is that margins and mfx both produce output that already closely resemble tidied regression output.
## Run a logistic regression
log_reg <- glm(am ~ cyl + hp + wt, data = mtcars, family = binomial)
## Tidy (but naive) coefficient values
library(broom)
tidy(log_reg)
#> # A tibble: 4 x 5
#> term estimate std.error statistic p.value
#> <chr> <dbl> <dbl> <dbl> <dbl>
#> 1 (Intercept) 19.7 8.12 2.43 0.0152
#> 2 cyl 0.488 1.07 0.455 0.649
#> 3 hp 0.0326 0.0189 1.73 0.0840
#> 4 wt -9.15 4.15 -2.20 0.0276
## Get the actual marginal effects instead
## Option 1: margins package
library(margins, quietly = T)
summary(margins(log_reg))
#> factor AME SE z p lower upper
#> cyl 0.0215 0.0470 0.4567 0.6479 -0.0706 0.1135
#> hp 0.0014 0.0006 2.3197 0.0204 0.0002 0.0026
#> wt -0.4025 0.1154 -3.4880 0.0005 -0.6287 -0.1764
## Option 2: mfx package
library(mfx, quietly = T, warn.conflicts = F)
logitmfx(log_reg, atmean = F, data = mtcars)
#> Call:
#> logitmfx(formula = log_reg, data = mtcars, atmean = F)
#>
#> Marginal Effects:
#> dF/dx Std. Err. z P>|z|
#> cyl 0.0214528 0.0499376 0.4296 0.6675
#> hp 0.0014339 0.0014602 0.9820 0.3261
#> wt -0.4025475 0.3782646 -1.0642 0.2872Created on 2019-05-02 by the reprex package (v0.2.1)