r - Obtaining Separate Summary Statistics by Categorical Variable with Stargazer Package

Question

I would like to use stargazer to produce summary statistics for each category of a grouping variable. I could do it in separate tables, but I'd like it all in one – if that is not unreasonably challenging for this package.

For example

library(stargazer)
stargazer(ToothGrowth, type = "text")
#> 
#> =========================================
#> Statistic N   Mean  St. Dev.  Min   Max  
#> -----------------------------------------
#> len       60 18.813  7.649   4.200 33.900
#> dose      60 1.167   0.629   0.500 2.000 
#> -----------------------------------------

provides summery statistics for the continues variables in ToothGrowth. I would like to split that summery by the categorical variable supp, also in ToothGrowth.

Two suggestions for desired outcome,

stargazer(ToothGrowth ~ supp, type = "text")
#> 
#> ==================================================
#> Statistic         N   Mean   St. Dev.  Min   Max  
#> --------------------------------------------------
#> OJ       len       30 16.963  8.266   4.200 33.900
#>          dose      30  1.167  0.634   0.500  2.000
#> VC       len       30 20.663  6.606   8.200 30.900
#>          dose      30  1.167  0.634   0.500  2.000 
#> --------------------------------------------------
#> 
 stargazer(ToothGrowth ~ supp, type = "text")
#> 
#> ==================================================
#> Statistic          N   Mean   St. Dev.  Min   Max  
#> --------------------------------------------------
#> len               
#>        _by VC     30 16.963  8.266   4.200 33.900
#>        _by VC     30  1.167  0.634   0.500  2.000
#> _tot              60 18.813  7.649   4.200 33.900
#> 
#> dose             
#>        _by OJ     30 20.663  6.606   8.200 30.900
#>        _by OJ     30  1.167  0.634   0.500  2.000 
#> _tot              60 1.167   0.629   0.500 2.000         
#> --------------------------------------------------

Answer 1

library(stargazer)
library(dplyr)
library(tidyr)

ToothGrowth %>%
    group_by(supp) %>%
    mutate(id = 1:n()) %>%
    ungroup() %>%
    gather(temp, val, len, dose) %>%
    unite(temp1, supp, temp, sep = '_') %>%
    spread(temp1, val) %>%
    select(-id) %>%
    as.data.frame() %>%
    stargazer(type = 'text')

Result

=========================================
Statistic N   Mean  St. Dev.  Min   Max  
-----------------------------------------
OJ_dose   30 1.167   0.634   0.500 2.000 
OJ_len    30 20.663  6.606   8.200 30.900
VC_dose   30 1.167   0.634   0.500 2.000 
VC_len    30 16.963  8.266   4.200 33.900
-----------------------------------------

Explanation

This gets rid of the problem mentioned by the OP in a comment to the original answer, "What I really want is a single table with summary statistics separated by a categorical variable instead of creating separate tables." The easiest way I saw to do that with stargazer was to create a new data frame that had variables for each group's observations using a gather(), unite(), spread() strategy. The only trick to it is to avoid duplicate identifiers by creating unique identifiers by group and dropping that variable before calling stargazer().