Standard Deviation in parenthesis: Latex R

Use some formatting function when you calculate sdPetal. For example,

library(tidyverse)
iris %>% group_by(Species) %>% summarize(MeanPetal = mean(Petal.Length), 
                                         sdPetal = sprintf("(%.2f)", sd(Petal.Length)))
#> `summarise()` ungrouping output (override with `.groups` argument)
#> # A tibble: 3 x 3
#>   Species    MeanPetal sdPetal
#>   <fct>          <dbl> <chr>  
#> 1 setosa          1.46 (0.17) 
#> 2 versicolor      4.26 (0.47) 
#> 3 virginica       5.55 (0.55)

^{Created on 2020-11-28 by the reprex package (v0.3.0)}

If you want this in LaTeX, just pass it through knitr::kable:

library(tidyverse)
library(knitr)
iris %>% 
    group_by(Species) %>% 
    summarize(MeanPetal = mean(Petal.Length), 
              sdPetal = sprintf("(%.2f)", sd(Petal.Length)),
              .groups = "keep") %>%
    kable(format = "latex") %>% cat
#> 
#> \begin{tabular}{l|r|l}
#> \hline
#> Species & MeanPetal & sdPetal\\
#> \hline
#> setosa & 1.462 & (0.17)\\
#> \hline
#> versicolor & 4.260 & (0.47)\\
#> \hline
#> virginica & 5.552 & (0.55)\\
#> \hline
#> \end{tabular}

^{Created on 2020-11-28 by the reprex package (v0.3.0)}

(You may or may not need the cat at the end, depending on how you are using this code. I needed it because I was producing Markdown code using reprex::reprex.)