Supporting Statistical Analysis for Research
4.6 Subsets of a data frame
Import the
PSID.csvdata set that was imported in the prior section.library(tidyverse)psid_path <- file.path("..", "datasets", "PSID.csv") psid_in <- read_csv(psid_path, col_types = cols())Warning: Missing column names filled in: 'X1' [1]psid_in <- rename( psid_in, obs_num = X1, intvw_num = intnum, person_id = persnum, marital_status = married ) psid <- psid_in glimpse(psid)Observations: 4,856 Variables: 9 $ obs_num <dbl> 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, ... $ intvw_num <dbl> 4, 4, 4, 4, 5, 6, 6, 7, 7, 7, 10, 10, 10, 11, 1... $ person_id <dbl> 4, 6, 7, 173, 2, 4, 172, 4, 170, 171, 3, 171, 1... $ age <dbl> 39, 35, 33, 39, 47, 44, 38, 38, 39, 37, 48, 47,... $ educatn <dbl> 12, 12, 12, 10, 9, 12, 16, 9, 12, 11, 13, 12, 1... $ earnings <dbl> 77250, 12000, 8000, 15000, 6500, 6500, 7000, 50... $ hours <dbl> 2940, 2040, 693, 1904, 1683, 2024, 1144, 2080, ... $ kids <dbl> 2, 2, 1, 2, 5, 2, 3, 4, 3, 5, 98, 3, 0, 0, 2, 0... $ marital_status <chr> "married", "divorced", "married", "married", "m...The obs_num variable is retained for these exaple. The examples of this section operate on row numbers and this variable has the row numbers.
Display the last three rows of the data frame using positional values to subset.
slice(psid, -1:-(n() - 3))# A tibble: 3 x 9 obs_num intvw_num person_id age educatn earnings hours kids <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> 1 4854 9302 1 37 8 22045 2793 98 2 4855 9305 2 40 6 134 30 3 3 4856 9306 2 37 17 33000 2423 4 # ... with 1 more variable: marital_status <chr>Displaying using the
tail()function to confirm the correct three rows are displayed.tail(psid)# A tibble: 6 x 9 obs_num intvw_num person_id age educatn earnings hours kids <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> 1 4851 9294 2 37 12 0 0 2 2 4852 9297 2 42 2 3000 1040 4 3 4853 9301 2 43 12 0 0 2 4 4854 9302 1 37 8 22045 2793 98 5 4855 9305 2 40 6 134 30 3 6 4856 9306 2 37 17 33000 2423 4 # ... with 1 more variable: marital_status <chr>Display the first, third, fifth, and seventh rows of columns two and three.
slice(psid, c(1, 3, 5, 7))# A tibble: 4 x 9 obs_num intvw_num person_id age educatn earnings hours kids <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> 1 1 4 4 39 12 77250 2940 2 2 3 4 7 33 12 8000 693 1 3 5 5 2 47 9 6500 1683 5 4 7 6 172 38 16 7000 1144 3 # ... with 1 more variable: marital_status <chr>or
psid[c(1, 3, 5, 7), ]# A tibble: 4 x 9 obs_num intvw_num person_id age educatn earnings hours kids <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> 1 1 4 4 39 12 77250 2940 2 2 3 4 7 33 12 8000 693 1 3 5 5 2 47 9 6500 1683 5 4 7 6 172 38 16 7000 1144 3 # ... with 1 more variable: marital_status <chr>Create a smaller data frame using the first 20 rows.
psid_small <- slice(psid, 1:20)or
psid_small <- psid[1:20, ]