compute standard deviation in R by sector

Question

i'm new to R and I'm sorry if this question is already answered. This is an example of my dataset:

idnumber SIC(1-digit) Year   Ebit
198       A           2019   2344
196       A           2019   6383
374       A           2019   5628
281       A           2019   2672
274       A           2018   2792
196       A           2018   3802
374       A           2018   3892
468       B           2019   6372
389       B           2019   3829
493       C           2019   2718
928       C           2019   2628
278       C           2019   3672

I want to compute the standard deviation for "Ebit" by the industrial sector "SIC(1-digit)". In this way I would like to find a volatility measure of operating revenue "Ebit" by industry.

Thanks in advance, for your kind answer..

`aggregate(df[,"Ebit"], by=list(df[,2]), FUN=sd)` . – maydin Mar 13 '21 at 15:39 — maydin, Mar 13 '21 at 15:39

score 1 · Accepted Answer · answered Mar 13 '21 at 17:50

Let's load your data to reproduce your example:

dat <- data.frame(
  idnumber = c(198, 196, 374, 281, 274, 196, 374, 468, 389, 493, 928, 278),
  `SIC(1-digit)` =  c('A', 'A', 'A', 'A', 'A', 'A', 'A', 'B', 'B', 'C', 'C', 'C'),
  Year = c(2019, 2019, 2019, 2019, 2018, 2018, 2018, 2019, 2019, 2019, 2019, 2019),
  Ebit = c(2344, 6383, 5628, 2672, 2792, 3802, 3892, 6372, 3829, 2718, 2628, 3672),
  check.names = FALSE
)

You see SIC(1-digit) is surrounded by back-ticks and the argument check.names = FALSE. This is because your column name has the special characters ( and ); you can read more about this here and here

Once your data is loaded, you can use dplyr:

library(dplyr)

dat %>% 
  group_by(`SIC(1-digit)`) %>%
  summarise(standard_deviation = sd(Ebit))


# A tibble: 3 x 2
  `SIC(1-digit)` standard_deviation
* <chr>                       <dbl>
1 A                           1544.
2 B                           1798.
3 C                            579.

Or data.table:

library(data.table)

setDT(dat)
dat[, .(standard_deviation = sd(Ebit)), by = `SIC(1-digit)`]

  
   SIC(1-digit) standard_deviation
1:            A          1544.4116
2:            B          1798.1725
3:            C           578.5257

compute standard deviation in R by sector

1 Answers1