Choose rows in a data.table

Choose rows in a data.table. Grouped data.tables grab rows within each group.

slice_head(.df, n = 5, ..., .by = NULL, by = NULL)

slice_tail(.df, n = 5, ..., .by = NULL, by = NULL)

slice_max(.df, order_by, n = 1, ..., with_ties = TRUE, .by = NULL, by = NULL)

slice_min(.df, order_by, n = 1, ..., with_ties = TRUE, .by = NULL, by = NULL)

slice(.df, ..., .by = NULL)

slice_sample(
  .df,
  n,
  prop,
  weight_by = NULL,
  replace = FALSE,
  .by = NULL,
  by = NULL
)

Arguments

.df

A data.frame or data.table

n

Number of rows to grab

...

Integer row values

.by, by

Columns to group by

order_by

Variable to arrange by

with_ties

Should ties be kept together. The default TRUE may return can return multiple rows if they are equal. Use FALSE to ignore ties.

prop

The proportion of rows to select

weight_by

Sampling weights

replace

Should sampling be performed with (TRUE) or without (FALSE, default) replacement

Examples

df <- data.table(
  x = 1:4,
  y = 5:8,
  z = c("a", "a", "a", "b")
)

df %>%
  slice(1:3)
#> # A tidytable: 3 × 3
#>       x     y z    
#>   <int> <int> <chr>
#> 1     1     5 a    
#> 2     2     6 a    
#> 3     3     7 a    

df %>%
  slice(1, 3)
#> # A tidytable: 2 × 3
#>       x     y z    
#>   <int> <int> <chr>
#> 1     1     5 a    
#> 2     3     7 a    

df %>%
  slice(1:2, .by = z)
#> # A tidytable: 3 × 3
#>       x     y z    
#>   <int> <int> <chr>
#> 1     1     5 a    
#> 2     2     6 a    
#> 3     4     8 b    

df %>%
  slice_head(1, .by = z)
#> # A tidytable: 2 × 3
#>       x     y z    
#>   <int> <int> <chr>
#> 1     1     5 a    
#> 2     4     8 b    

df %>%
  slice_tail(1, .by = z)
#> # A tidytable: 2 × 3
#>       x     y z    
#>   <int> <int> <chr>
#> 1     3     7 a    
#> 2     4     8 b    

df %>%
  slice_max(order_by = x, .by = z)
#> # A tidytable: 2 × 3
#>       x     y z    
#>   <int> <int> <chr>
#> 1     4     8 b    
#> 2     3     7 a    

df %>%
  slice_min(order_by = y, .by = z)
#> # A tidytable: 2 × 3
#>       x     y z    
#>   <int> <int> <chr>
#> 1     1     5 a    
#> 2     4     8 b