Extract tables and lists

xml_table() turns table elements into data frames, and xml_list() turns ul and ol elements into R lists. Both read well-formed XML, such as XHTML or a table embedded in another XML format. They do not apply HTML parsing rules: a table without tbody has exactly the rows it contains.

Usage

xml_table(x, header = NA, trim = TRUE, ns = NULL, max_cells = 1e+07)

xml_list(x, trim = TRUE, ns = NULL)

Arguments

x

A node or nodeset of table elements for xml_table(), or of ul and ol elements for xml_list(). A document stands for its root.

header

Use the first row as column names. NA, the default, does so when every cell of the first row is a th.

trim

Trim leading and trailing whitespace from each value.

ns

Namespace URI of the table or list elements, NA for none, NULL for any.

max_cells

The most cells one table may expand to. A positive whole number, or Inf.

Value

A list with one element per node in x: a data frame for xml_table(), a list of items for xml_list().

Details

Tables. The rows are the tr elements that are children of the table, or of its thead, tbody or tfoot, in document order. A table nested inside a cell is not descended into; extract it separately. The cells are the td and th elements of a row, and a cell's value is its text, as xml_text() gives it. Every column is character: convert types yourself, for example with type.convert(df, as.is = TRUE).

colspan and rowspan are expanded by repeating the cell's value. A span that is not a positive whole number counts as 1, and spans are capped at HTML's own limits, 1000 columns and 65534 rows. A row span never adds rows past the end of the table. Short rows are padded with NA.

Expansion can make a small document produce a very large table, so the expanded size of each table is bounded by max_cells, and exceeding it is a zuxml_limit_error.

Lists. Each li child of a ul or ol becomes one item. An item is its text as a string or, when the li has ul or ol children, a list with two elements: text, the item's own text without the nested lists', and items, the items of its nested lists, extracted the same way. Only direct ul and ol children of an li count as nested lists. Comments and processing instructions inside an item are ignored.

See also

xml_find() to locate the tables or lists in a document, and zuxml-conditions for the errors these raise.

Examples

doc <- xml_parse("<table>
  <tr><th>fruit</th><th>price</th></tr>
  <tr><td>apple</td><td>1.20</td></tr>
  <tr><td>pear</td><td>0.90</td></tr>
</table>")
xml_table(xml_root(doc))[[1]]
#>   fruit price
#> 1 apple  1.20
#> 2  pear  0.90

doc <- xml_parse("<ul>
  <li>fruit<ul><li>apple</li><li>pear</li></ul></li>
  <li>bread</li>
</ul>")
str(xml_list(xml_root(doc))[[1]])
#> List of 2
#>  $ :List of 2
#>   ..$ text : chr "fruit"
#>   ..$ items:List of 2
#>   .. ..$ : chr "apple"
#>   .. ..$ : chr "pear"
#>  $ : chr "bread"