h5_length: Get the Total Length of an HDF5 Object or Attribute
In h5lite: Simplified 'HDF5' Interface

h5_length

R Documentation

Get the Total Length of an HDF5 Object or Attribute

Description

Behaves like length() for R objects.

For Compound Datasets (data.frames), this is the number of columns.
For Datasets and Attributes, this is the product of all dimensions (total number of elements).
For Groups, this is the number of objects directly contained in the group.
Scalar datasets or attributes return 1.

Usage

h5_length(file, name, attr = NULL)

Arguments

`file`	The path to the HDF5 file.
`name`	The full path of the object (group or dataset).
`attr`	The name of an attribute to check. If provided, the length of the attribute is returned.

Value

An numeric scalar representing the total length (number of elements).

Examples

file <- tempfile(fileext = ".h5")

h5_write(1:100, file, "my_vec")
h5_length(file, "my_vec") # 100

h5_write(mtcars, file, "my_df")
h5_length(file, "my_df") # 11 (ncol(mtcars))

h5_write(as.matrix(mtcars), file, "my_mtx")
h5_length(file, "my_mtx") # 352 (prod(dim(mtcars)))

h5_length(file, "/") # 3

unlink(file)

h5lite documentation built on May 19, 2026, 1:07 a.m.