Obtaining Separate Summary Statistics by Categorical Variable with Stargazer Package

Solution

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().

Three possible solution. One using reporttools and xtable, one using tidyverse tools along with stargazer, and third a base-r solution.

First,

I want to suggest you take a look at reporttools which is kinda leaving stargazer, but I think you should take a look at it,

# install.packages("reporttools")  #Use this to install it, do this only once
require(reporttools)

vars <- ToothGrowth[,c('len','dose')]
group <- ToothGrowth[,c('supp')]

## display default statistics, only use a subset of observations, grouped analysis
tableContinuous(vars = vars, group = group, prec = 1, cap = "Table of 'len','dose' by 'supp' ", lab = "tab: descr stat")

% latex table generated in R 3.3.3 by xtable 1.8-2 package
\begingroup\footnotesize
\begin{longtable}{llrrrrrrrrrr}
 \textbf{Variable} & \textbf{Levels} & $\mathbf{n}$ & \textbf{Min} & $\mathbf{q_1}$ & $\mathbf{\widetilde{x}}$ & $\mathbf{\bar{x}}$ & $\mathbf{q_3}$ & \textbf{Max} & $\mathbf{s}$ & \textbf{IQR} & \textbf{\#NA} \\ 
  \hline
len & OJ & 30 & 8.2 & 15.5 & 22.7 & 20.7 & 25.7 & 30.9 & 6.6 & 10.2 & 0 \\ 
   & VC & 30 & 4.2 & 11.2 & 16.5 & 17.0 & 23.1 & 33.9 & 8.3 & 11.9 & 0 \\ 
   \hline
 & all & 60 & 4.2 & 13.1 & 19.2 & 18.8 & 25.3 & 33.9 & 7.6 & 12.2 & 0 \\ 
   \hline
dose & OJ & 30 & 0.5 &  0.5 &  1.0 &  1.2 &  2.0 &  2.0 & 0.6 &  1.5 & 0 \\ 
   & VC & 30 & 0.5 &  0.5 &  1.0 &  1.2 &  2.0 &  2.0 & 0.6 &  1.5 & 0 \\ 
   \hline
 & all & 60 & 0.5 &  0.5 &  1.0 &  1.2 &  2.0 &  2.0 & 0.6 &  1.5 & 0 \\ 
   \hline
\hline
\caption{Table of 'len','dose' by 'supp' } 
\label{tab: descr stat}
\end{longtable}
\endgroup

in latex you get this nice result,

Second,

using tidyverse tools along with stargazer, inspired by this SO answer,

# install.packages(c("tidyverse"), dependencies = TRUE)
library(dplyr); library(purrr)
#> ToothGrowth %>% split(. $supp) %>% walk(~ stargazer(., type = "text"))
#> =========================================
#> Statistic N   Mean  St. Dev.  Min   Max  
#> -----------------------------------------
#> len       30 20.663  6.606   8.200 30.900
#> dose      30 1.167   0.634   0.500 2.000 
#> -----------------------------------------
#> =========================================
#> Statistic N   Mean  St. Dev.  Min   Max  
#> -----------------------------------------
#> len       30 16.963  8.266   4.200 33.900
#> dose      30 1.167   0.634   0.500 2.000 
#> -----------------------------------------
#> 

Third,

an exclusive base-r

by(ToothGrowth, ToothGrowth$supp, stargazer, type = 'text')
    #> =========================================
    #> Statistic N   Mean  St. Dev.  Min   Max  
    #> -----------------------------------------
    #> len       30 20.663  6.606   8.200 30.900
    #> dose      30 1.167   0.634   0.500 2.000 
    #> -----------------------------------------
    #> 
    #> =========================================
    #> Statistic N   Mean  St. Dev.  Min   Max  
    #> -----------------------------------------
    #> len       30 16.963  8.266   4.200 33.900
    #> dose      30 1.167   0.634   0.500 2.000 
    #> -----------------------------------------
    #> ToothGrowth$supp: OJ
    #> [1] ""                                         
    #> [2] "========================================="
    #> [3] "Statistic N   Mean  St. Dev.  Min   Max  "
    #> [4] "-----------------------------------------"
    #> [5] "len       30 20.663  6.606   8.200 30.900"
    #> [6] "dose      30 1.167   0.634   0.500 2.000 "
    #> [7] "-----------------------------------------"
    #> --------------------------------------------------------------- 
    #> ToothGrowth$supp: VC
    #> [1] ""                                         
    #> [2] "========================================="
    #> [3] "Statistic N   Mean  St. Dev.  Min   Max  "
    #> [4] "-----------------------------------------"
    #> [5] "len       30 16.963  8.266   4.200 33.900"
    #> [6] "dose      30 1.167   0.634   0.500 2.000 "
    #> [7] "-----------------------------------------"