tidyfst (version 1.8.1)

slice_dt: Subset rows using their positions

Description

`slice_dt()` lets you index rows by their (integer) locations. It allows you to select, remove, and duplicate rows. It is accompanied by a number of helpers for common use cases:

* `slice_head_dt()` and `slice_tail_dt()` select the first or last rows. * `slice_sample_dt()` randomly selects rows. * `slice_min_dt()` and `slice_max_dt()` select rows with highest or lowest values of a variable.

Usage

slice_dt(.data, ..., by = NULL)
slice_head_dt(.data, n, by = NULL)
slice_tail_dt(.data, n, by = NULL)
slice_max_dt(.data, order_by, n, by = NULL, with_ties = TRUE)
slice_min_dt(.data, order_by, n, by = NULL, with_ties = TRUE)
slice_sample_dt(.data, n, replace = FALSE, by = NULL)

Value

A data.table

Arguments

.data

A data.table

...

Provide either positive values to keep, or negative values to drop. The values provided must be either all positive or all negative.

by

Slice by which group(s)?

n

When larger than or equal to 1, the number of rows. When between 0 and 1, the proportion of rows to select.

order_by

Variable or function of variables to order by.

with_ties

Should ties be kept together? The default, `TRUE`, may return more rows than you request. Use `FALSE` to ignore ties, and return the first `n` rows.

replace

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

See Also

slice

Examples

a = iris
slice_dt(a,1,2)
slice_dt(a,2:3)
slice_dt(a,141:.N)
slice_dt(a,1,.N)
slice_head_dt(a,5)
slice_head_dt(a,0.1)
slice_tail_dt(a,5)
slice_tail_dt(a,0.1)
slice_max_dt(a,Sepal.Length,10)
slice_max_dt(a,Sepal.Length,10,with_ties = FALSE)
slice_min_dt(a,Sepal.Length,10)
slice_min_dt(a,Sepal.Length,10,with_ties = FALSE)
slice_sample_dt(a,10)
slice_sample_dt(a,0.1)


# use by to slice by group

## following codes get the same results
slice_dt(a,1:3,by = "Species")
slice_dt(a,1:3,by = Species)
slice_dt(a,1:3,by = .(Species))

slice_head_dt(a,2,by = Species)
slice_tail_dt(a,2,by = Species)

slice_max_dt(a,Sepal.Length,3,by = Species)
slice_max_dt(a,Sepal.Length,3,by = Species,with_ties = FALSE)
slice_min_dt(a,Sepal.Length,3,by = Species)
slice_min_dt(a,Sepal.Length,3,by = Species,with_ties = FALSE)

# in `slice_sample_dt`, "by" could only take character class
slice_sample_dt(a,.1,by = "Species")
slice_sample_dt(a,3,by = "Species")
slice_sample_dt(a,51,replace = TRUE,by = "Species")