Pivotlongercols

Pivotlongercols is an informal term used in data tidying to describe the set of column names chosen for a pivot_longer operation. It is not a standalone function in the tidyr package; rather, it refers to the collection of columns supplied to the cols argument of pivot_longer. In practice, pivotlongercols are selected with tidyselect helpers such as starts_with, ends_with, contains, matches, or with a direct vector of column names.

Overview and purpose

The concept helps document and discuss which wide-format columns are being transformed into a long format. By using tidyselect expressions within cols, analysts can specify patterns or groups of related columns, enabling scalable reshaping of datasets with many similarly named measurements.

Usage and syntax

Pivot_longer in tidyr is invoked with a cols parameter that determines which columns to pivot. Examples of selectors include:

- cols = starts_with("score_")

- cols = matches("\\d{4}$")

- cols = contains("measurement")

Example

Suppose a data frame has columns like A_2018, A_2019, B_2018, B_2019. A typical long format transformation would be:

pivot_longer(df, cols = matches("^(A|B)_"), names_to = c("group", "year"), names_sep = "_", values_to = "value")

Here, the pivotlongercols are the columns matched by the selector, gathered into two new keys.

Relation to other concepts

Pivotlongercols is distinct from a built-in function; it is a descriptive label for the columns selected for pivot_longer. It complements the official pivot_longer API and relies on tidyselect mechanisms to define the column set.

See also

pivot_longer, tidyr, tidyverse, tidyselect.