as_cells: Tokenize data frames into a tidy 'melted' structure

In unpivotr: Unpivot Complex and Irregular Data Layouts

Tokenize data frames into a tidy 'melted' structure

Description

Data frames represent data in a tabular structure. as_cells() takes the row and column position of each 'cell', and returns that information in a new data frame, alongside the content and type of each cell.

This makes it easier to deal with complex or non-tabular data (e.g. pivot tables) that have been imported into R as data frames. Once they have been 'melted' by as_cells(), you can use functions like behead() and spatter() to reshape them into conventional, tidy, unpivoted structures.

For HTML tables, the content of each cell is returned as a standalone HTML string that can be further parsed with tools such as the rvest package. This is particularly useful when an HTML cell itself contains an HTML table, or contains both text and a URL. If the HTML itself is poorly formatted, try passing it through the htmltidy package first.

This is an S3 generic.

Usage

as_cells(x, row_names = FALSE, col_names = FALSE)

Arguments

x	A data.frame or an HTML document
row_names	Whether to treat the row names as cells, Default: FALSE
col_names	Whether to treat the column names as cells, Default: FALSE

Details

For certain non-rectangular data formats, it can be useful to parse the data into a melted format where each row represents a single token.

Value

A data.frame with the following columns:

• row and col (integer) giving the original position of the 'cells'

• any relevant columns for cell values in their original types: chr, cplx, cplx, dbl, fct, int, lgl, list, and ord

• data_type to specify for each cell which of the above columns (chr etc.) the value is in.

The columns fct and ord are, like list, list-columns (each element is independent) to avoid factor levels clashing. For HTML tables, the column html gives the HTML string of the original cell.

Row and column names, when present and required by row_names = TRUE or col_names = TRUE, are treated as though they were cells in the table, and they appear in the chr column.

Examples

x <- data.frame(a = c(10, 20),
                b = c("foo", "bar"),
                stringsAsFactors = FALSE)
x
as_cells(x)
as_cells(x, row_names = TRUE)
as_cells(x, col_names = TRUE)

# 'list' columns are undisturbed
y <- data.frame(a = c("a", "b"), stringsAsFactors = FALSE)
y$b <- list(1:2, 3:4)
y
as_cells(y)

# Factors are preserved by being wrapped in lists so that their levels don't
# conflict.  Blanks are NULLs.
z <- data.frame(x = factor(c("a", "b")),
                y = factor(c("c", "d"), ordered = TRUE))
as_cells(z)
as_cells(z)$fct
as_cells(z)$ord

# HTML tables can be extracted from the output of xml2::read_html().  These
# are returned as a list of tables, similar to rvest::html_table().  The
# value of each cell is its standalone HTML string, which can contain
# anything -- even another table.

colspan <- system.file("extdata", "colspan.html", package = "unpivotr")
rowspan <- system.file("extdata", "rowspan.html", package = "unpivotr")
nested <- system.file("extdata", "nested.html", package = "unpivotr")

## Not run: 
browseURL(colspan)
browseURL(rowspan)
browseURL(nestedspan)

## End(Not run)

as_cells(xml2::read_html(colspan))
as_cells(xml2::read_html(rowspan))
as_cells(xml2::read_html(nested))

unpivotr documentation built on Jan. 23, 2023, 5:40 p.m.