slice_dt {tidyfst}

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)

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.

Value

A data.table

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")