Title:	Simplified 'HDF5' Interface
Version:	2.0.0.2
Description:	A user-friendly interface for the Hierarchical Data Format 5 ('HDF5') library designed to "just work." It bundles the necessary system libraries to ensure easy installation on all platforms. Features smart defaults that automatically map R objects (vectors, matrices, data frames) to efficient 'HDF5' types, removing the need to manage low-level details like dataspaces or property lists. Uses the 'HDF5' library developed by The HDF Group https://www.hdfgroup.org/.
URL:	https://github.com/cmmr/h5lite, https://cmmr.github.io/h5lite/
BugReports:	https://github.com/cmmr/h5lite/issues
Depends:	R (≥ 4.2.0)
LinkingTo:	hdf5lib (≥ 2.0.0.5)
Suggests:	bit64, knitr, rmarkdown, testthat (≥ 3.0.0)
NeedsCompilation:	yes
License:	MIT + file LICENSE
Encoding:	UTF-8
Config/testthat/edition:	3
Config/Needs/website:	rmarkdown
RoxygenNote:	7.3.3
VignetteBuilder:	knitr
Packaged:	2026-01-25 20:50:23 UTC; Daniel
Author:	Daniel P. Smith [aut, cre], Alkek Center for Metagenomics and Microbiome Research [cph, fnd]
Maintainer:	Daniel P. Smith <dansmith01@gmail.com>
Repository:	CRAN
Date/Publication:	2026-01-29 20:20:07 UTC

h5lite: A Simple and Lightweight HDF5 Interface

Description

The h5lite package provides a simple, lightweight, and user-friendly interface for reading and writing HDF5 files. It is designed for R users who want to save and load common R objects (vectors, matrices, arrays, factors, and data.frames) to an HDF5 file without needing to understand the low-level details of the HDF5 C API.

Key Features

• Simple API: Use familiar functions like h5_read() and h5_write().

• Automatic Handling: Dimensions, data types, and group creation are handled automatically.

• Safe by Default: Auto-selects a safe R data type for numeric data to prevent overflow.

• Easy Installation: The required HDF5 library is bundled with the package.

Author(s)

Maintainer: Daniel P. Smith dansmith01@gmail.com (ORCID)

Other contributors:

• Alkek Center for Metagenomics and Microbiome Research [copyright holder, funder]

See Also

Useful links:

• https://cmmr.github.io/h5lite/

• Report bugs at https://github.com/cmmr/h5lite/issues

Key functions: h5_read(), h5_write(), h5_ls(), h5_str()

List HDF5 Attributes

Description

Lists the names of attributes attached to a specific HDF5 object.

Usage

h5_attr_names(file, name = "/")

Arguments

Value

A character vector of attribute names.

See Also

h5_ls()

Examples

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

h5_write(1:10,          file, "data")
h5_write(I("meters"),   file, "data", attr = "unit")
h5_write(I(Sys.time()), file, "data", attr = "timestamp")

h5_attr_names(file, "data") # "unit" "timestamp"

unlink(file)

Get R Class of an HDF5 Object or Attribute

Description

Inspects an HDF5 object (or an attribute attached to it) and returns the R class that h5_read() would produce.

Usage

h5_class(file, name, attr = NULL)

Arguments

Details

This function determines the resulting R class by inspecting the storage metadata.

• Group \rightarrow "list"

• Integer \rightarrow "numeric"

• Floating Point \rightarrow "numeric"

• String \rightarrow "character"

• Complex \rightarrow "complex"

• Enum \rightarrow "factor"

• Opaque \rightarrow "raw"

• Compound \rightarrow "data.frame"

• Null \rightarrow "NULL"

Value

A character string representing the R class (e.g., "integer", "numeric", "complex", "character", "factor", "raw", "list", "NULL"). Returns NA_character_ for HDF5 types that h5lite cannot read.

See Also

h5_typeof(), h5_read()

Examples

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

h5_write(1:10, file, "my_ints", as = "int32")
h5_class(file, "my_ints") # "numeric"

h5_write(mtcars, file, "mtcars")
h5_class(file, "mtcars") # "data.frame"

h5_write(c("a", "b", "c"), file, "strings")
h5_class(file, "strings") # "character"

h5_write(c(1, 2, 3), file, "my_floats", as = "float64")
h5_class(file, "my_floats") # "numeric"

unlink(file)

Create an HDF5 File

Description

Explicitly creates a new, empty HDF5 file.

Usage

h5_create_file(file)

Arguments

Details

This function is a simple wrapper around h5_create_group(file, "/"). Its main purpose is to allow for explicit file creation in code.

Note that calling this function is almost always unnecessary, as all h5lite writing functions (like h5_write() or h5_create_group()) will automatically create the file if it does not exist.

It is provided as a convenience for users who prefer to explicitly create a file before writing data to it.

Value

Invisibly returns NULL. This function is called for its side effects.

File Handling

• If file does not exist, it will be created as a new, empty HDF5 file.

• If file already exists and is a valid HDF5 file, this function does nothing and returns successfully.

• If file exists but is not a valid HDF5 file (e.g., a text file), an error will be thrown and the file will not be modified.

See Also

h5_create_group(), h5_write()

Examples

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

# Explicitly create the file
h5_create_file(file)

if (file.exists(file)) {
  message("File created successfully.")
}

unlink(file)

Create an HDF5 Group

Description

Explicitly creates a new group (or nested groups) in an HDF5 file. This is useful for creating an empty group structure.

Usage

h5_create_group(file, name)

Arguments

Value

Invisibly returns NULL. This function is called for its side effects.

Examples

file <- tempfile(fileext = ".h5")
h5_create_file(file)

# Create a nested group structure
h5_create_group(file, "/data/experiment/run1")
h5_ls(file)

unlink(file)

Delete an HDF5 Object or Attribute

Description

Deletes an object (dataset or group) or an attribute from an HDF5 file. If the object or attribute does not exist, a warning is issued and the function returns successfully (no error is raised).

Usage

h5_delete(file, name, attr = NULL, warn = TRUE)

Arguments

Value

Invisibly returns NULL. This function is called for its side effects.

See Also

h5_create_group(), h5_move()

Examples

file <- tempfile(fileext = ".h5")
h5_create_file(file)

# Create some data and attributes
h5_write(matrix(1:10, 2, 5), file, "matrix")
h5_write("A note", file, "matrix", attr = "note")

# Review the file structure
h5_str(file)

# Delete the attribute
h5_delete(file, "matrix", attr = "note")

# Review the file structure
h5_str(file)

# Delete the dataset
h5_delete(file, "matrix")

# Review the file structure
h5_str(file)

# Cleaning up
unlink(file)

Get Dimensions of an HDF5 Object or Attribute

Description

Returns the dimensions of a dataset or an attribute as an integer vector. These dimensions match the R-style (column-major) interpretation.

Usage

h5_dim(file, name, attr = NULL)

Arguments

Value

An integer vector of dimensions, or integer(0) for scalars.

Examples

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

h5_write(matrix(1:10, 2, 5), file, "matrix")
h5_dim(file, "matrix") # 2 5

h5_write(mtcars, file, "mtcars")
h5_dim(file, "mtcars") # 32 11

h5_write(I(TRUE), file, "my_bool")
h5_dim(file, "my_bool") # integer(0)

h5_write(1:10, file, "my_ints")
h5_dim(file, "my_ints") # 10

unlink(file)

Check if an HDF5 File, Object, or Attribute Exists

Description

Safely checks if a file, an object within a file, or an attribute on an object exists.

Usage

h5_exists(file, name = "/", attr = NULL, assert = FALSE)

Arguments

Details

This function provides a robust, error-free way to test for existence.

• Testing for a File: If name is / and attr is NULL, the function checks if file is a valid, readable HDF5 file.

• Testing for an Object: If name is a path (e.g., ⁠/data/matrix⁠) and attr is NULL, the function checks if the specific object exists.

• Testing for an Attribute: If attr is provided, the function checks if that attribute exists on the specified object name.

Value

A logical value: TRUE if the target exists and is valid, FALSE otherwise.

See Also

h5_is_group(), h5_is_dataset()

Examples

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

h5_exists(file) # FALSE

h5_create_file(file)
h5_exists(file) # TRUE

h5_exists(file, "missing_object") # FALSE

h5_write(1:10, file, "my_ints")
h5_exists(file, "my_ints") # TRUE

h5_exists(file, "my_ints", "missing_attr") # FALSE

h5_write(1:10, file, "my_ints", attr = "my_attr")
h5_exists(file, "my_ints", "my_attr") # TRUE

unlink(file)

Check if an HDF5 Object is a Dataset

Description

Checks if the object at a given path is a dataset.

Usage

h5_is_dataset(file, name, attr = NULL)

Arguments

Value

A logical value: TRUE if the object exists and is a dataset, FALSE otherwise (if it is a group, or does not exist).

See Also

h5_is_group(), h5_exists()

Examples

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

h5_write(1, file, "dset")
h5_is_dataset(file, "dset") # TRUE

h5_create_group(file, "grp")
h5_is_dataset(file, "grp") # FALSE

h5_write(1, file, "grp", attr = "my_attr")
h5_is_dataset(file, "grp", "my_attr") # TRUE

unlink(file)

Check if an HDF5 Object is a Group

Description

Checks if the object at a given path is a group.

Usage

h5_is_group(file, name, attr = NULL)

Arguments

Value

A logical value: TRUE if the object exists and is a group, FALSE otherwise (if it is a dataset, or does not exist).

See Also

h5_is_dataset(), h5_exists()

Examples

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

h5_create_group(file, "grp")
h5_is_group(file, "grp") # TRUE

h5_write(1:10, file, "my_ints")
h5_is_group(file, "my_ints") # FALSE

unlink(file)

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

Value

An integer 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)

List HDF5 Objects

Description

Lists the names of objects (datasets and groups) within an HDF5 file or group.

Usage

h5_ls(file, name = "/", recursive = TRUE, full.names = FALSE, scales = FALSE)

Arguments

Value

A character vector of object names. If name is / (the default), the paths are relative to the root of the file. If name is another group, the paths are relative to that group (unless full.names = TRUE).

See Also

h5_attr_names(), h5_str()

Examples

file <- tempfile(fileext = ".h5")
h5_create_group(file, "foo/bar")
h5_write(1:5, file, "foo/data")

# List everything recursively
h5_ls(file)

# List only top-level objects
h5_ls(file, recursive = FALSE)

# List relative to a sub-group
h5_ls(file, "foo")

unlink(file)

Move or Rename an HDF5 Object

Description

Moves or renames an object (dataset, group, etc.) within an HDF5 file.

Usage

h5_move(file, from, to)

Arguments

Details

This function provides an efficient, low-level wrapper for the HDF5 library's H5Lmove function. It is a metadata-only operation, meaning the data itself is not read or rewritten. This makes it extremely fast, even for very large datasets.

You can use this function to either rename an object within the same group (e.g., "data/old" to "data/new") or to move an object to a different group (e.g., "data/old" to "archive/old"). The destination parent group will be automatically created if it does not exist.

Value

This function is called for its side-effect and returns NULL invisibly.

See Also

h5_create_group(), h5_delete()

Examples

file <- tempfile(fileext = ".h5")
h5_write(1:10, file, "group/dataset")

# Review the file structure
h5_str(file)

# Rename within the same group
h5_move(file, "group/dataset", "group/renamed")

# Review the file structure
h5_str(file)

# Move to a new group (creates parent automatically)
h5_move(file, "group/renamed", "archive/dataset")

# Review the file structure
h5_str(file)

unlink(file)

Get Names of an HDF5 Object

Description

Returns the names of the object.

• For Groups, it returns the names of the objects contained in the group (similar to ls()).

• For Compound Datasets (data.frames), it returns the column names.

• For other Datasets, it looks for a dimension scale and returns it if found.

Usage

h5_names(file, name = "/", attr = NULL)

Arguments

Value

A character vector of names, or NULL if the object has no names.

Examples

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

h5_write(data.frame(x=1, y=2), file, "df")
h5_names(file, "df") # "x" "y"

x <- 1:5
names(x) <- letters[1:5]
h5_write(x, file, "x")
h5_names(file, "x") # "a" "b" "c" "d" "e"

h5_write(mtcars[,c("mpg", "hp")], file, "dset")
h5_names(file, "dset") # "mpg" "hp"

unlink(file)

Create an HDF5 File Handle

Description

Creates a file handle that provides a convenient, object-oriented interface for interacting with and navigating a specific HDF5 file.

Usage

h5_open(file)

Arguments

Details

This function returns a special h5 object that wraps the standard h5lite functions. The primary benefit is that the file argument is pre-filled, allowing for more concise and readable code when performing multiple operations on the same file.

For example, instead of writing:

h5_write(1:10, file, "dset1")
h5_write(2:20, file, "dset2")
h5_ls(file)

You can create a handle and use its methods. Note that the file argument is omitted from the method calls:

h5 <- h5_open("my_file.h5")
h5$write(1:10, "dset1")
h5$write(2:20, "dset2")
h5$ls()
h5$close()

Value

An object of class h5 with methods for interacting with the file.

Pass-by-Reference Behavior

Unlike most R objects, the h5 handle is an environment. This means it is passed by reference. If you assign it to another variable (e.g., h5_alias <- h5), both variables point to the same handle. Modifying one (e.g., by calling h5_alias$close()) will also affect the other.

Interacting with the HDF5 File

The h5 object provides several ways to interact with the HDF5 file:

Standard h5lite Functions as Methods

Most h5lite functions (e.g., h5_read, h5_write, h5_ls) are available as methods on the h5 object, without the h5_ prefix.

For example, h5$write(data, "dset") is equivalent to h5_write(data, file, "dset").

The available methods are: attr_names, cd, class, close, create_group, delete, dim, exists, is_dataset, is_group, length, ls, move, names, pwd, read, str, typeof, write.

Navigation (⁠$cd()⁠, ⁠$pwd()⁠)

The handle maintains an internal working directory to simplify path management.

• h5$cd(group): Changes the handle's internal working directory. This is a stateful, pass-by-reference operation. It understands absolute paths (e.g., "/new/path") and relative navigation (e.g., "../other"). The target group does not need to exist.

• h5$pwd(): Returns the current working directory.

When you call a method like h5$read("dset"), the handle automatically prepends the current working directory to any relative path. If you provide an absolute path (e.g., h5$read("/path/to/dset")), the working directory is ignored.

Closing the Handle (⁠$close()⁠)

The h5lite package does not keep files persistently open. Each operation opens, modifies, and closes the file. Therefore, the h5$close() method does not perform any action on the HDF5 file itself.

Its purpose is to invalidate the handle, preventing any further operations from being called. After h5$close() is called, any subsequent method call (e.g., h5$ls()) will throw an error.

Examples

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

# Open the handle
h5 <- h5_open(file)

# Write data (note: 'data' is the first argument, 'file' is implicit)
h5$write(1:5, "vector")
h5$write(matrix(1:9, 3, 3), "matrix")

# Create a group and navigate to it
h5$create_group("simulations")
h5$cd("simulations")
print(h5$pwd()) # "/simulations"

# Write data relative to the current working directory
h5$write(rnorm(10), "run1") # Writes to /simulations/run1

# Read data
dat <- h5$read("run1")

# List contents of current WD
h5$ls()

# Close the handle
h5$close()
unlink(file)

Read an HDF5 Object or Attribute

Description

Reads a dataset, a group, or a specific attribute from an HDF5 file into an R object.

Usage

h5_read(file, name = "/", attr = NULL, as = "auto")

Arguments

Value

An R object corresponding to the HDF5 object or attribute. Returns NULL if the object is skipped via as = "null".

Type Conversion (as)

You can control how HDF5 data is converted to R types using the as argument.

1. Mapping by Name:

• as = c("data_col" = "integer"): Reads the dataset/column named "data_col" as an integer.

• as = c("@validated" = "logical"): When reading a dataset, this forces the attached attribute "validated" to be read as logical.

2. Mapping by HDF5 Type Class: You can target specific HDF5 data types using keys prefixed with a dot (.). Supported classes include:

• Integer: .int, .int8, .int16, .int32, .int64

• Unsigned: .uint, .uint8, .uint16, .uint32, .uint64

• Floating Point: .float, .float16, .float32, .float64

Example: as = c(.uint8 = "logical", .int = "bit64")

3. Precedence & Attribute Config:

• Attributes vs Datasets: Attribute type mappings take precedence over dataset mappings. If you specify as = c(.uint = "logical", "@.uint" = "integer"), unsigned integer datasets will be read as logical, but unsigned integer attributes will be read as integer.

• Specific vs Generic: Specific keys (e.g., .uint32) take precedence over generic keys (e.g., .uint), which take precedence over the global default (.).

Note

The @ prefix is only used to configure attached attributes when reading a dataset (attr = NULL). If you are reading a specific attribute directly (e.g., h5_read(..., attr = "id")), do not use the @ prefix in the as argument.

See Also

h5_write()

Examples

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

# --- Write Data ---
h5_write(c(10L, 20L), file, "ints")
h5_write(I(TRUE),     file, "ints", attr = "ready")
h5_write(c(10.5, 18), file, "floats")
h5_write(I("meters"), file, "floats", attr = "unit")

# --- Read Data ---
# Read dataset
x <- h5_read(file, "ints")
print(x)

# Read dataset with attributes
y <- h5_read(file, "floats")
print(attr(y, "unit"))

# Read a specific attribute directly
unit <- h5_read(file, "floats", attr = "unit")
print(unit)

# --- Type Conversion Examples ---

# Force integer dataset to be read as numeric (double)
x_dbl <- h5_read(file, "ints", as = "double")
class(x_dbl)

# Force attached attribute to be read as logical
# Note the "@" prefix to target the attribute
z <- h5_read(file, "ints", as = c("@ready" = "logical"))
print(z)

unlink(file)

Display the Structure of an HDF5 Object

Description

Recursively prints a summary of an HDF5 group or dataset, similar to the structure of h5ls -r. It displays the nested structure, object types, dimensions, and attributes.

Usage

h5_str(file, name = "/", attrs = TRUE, members = TRUE, markup = interactive())

Arguments

Details

This function provides a quick and convenient way to inspect the contents of an HDF5 file. It performs a recursive traversal of the file from the C-level and prints a formatted summary to the R console.

This function does not read any data into R. It only inspects the metadata (names, types, dimensions) of the objects in the file, making it fast and memory-safe for arbitrarily large files.

Value

This function is called for its side-effect of printing to the console and returns NULL invisibly.

See Also

h5_ls(), h5_attr_names()

Examples

file <- tempfile(fileext = ".h5")
h5_write(list(x = 1:10, y = matrix(1:9, 3, 3)), file, "group")
h5_write("metadata", file, "group", attr = "info")

# Print structure
h5_str(file)

unlink(file)

Get HDF5 Storage Type of an Object or Attribute

Description

Returns the low-level HDF5 storage type of a dataset or an attribute (e.g., "int8", "float64", "utf8", "ascii[10]"). This allows inspecting the file storage type before reading the data into R.

Usage

h5_typeof(file, name, attr = NULL)

Arguments

Value

A character string representing the HDF5 storage type (e.g., "float32", "uint32", "ascii[10]", "compound[2]").

See Also

h5_class(), h5_exists()

Examples

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

h5_write(1L, file, "int32_val", as = "int32")
h5_typeof(file, "int32_val") # "int32"

h5_write(mtcars, file, "mtcars")
h5_typeof(file, "mtcars") # "compound[11]"

h5_write(c("a", "b", "c"), file, "strings")
h5_typeof(file, "strings") # "utf8[1]"

unlink(file)

Write an R Object to HDF5

Description

Writes an R object to an HDF5 file, creating the file if it does not exist. This function acts as a unified writer for datasets, groups (lists), and attributes.

Usage

h5_write(data, file, name, attr = NULL, as = "auto", compress = TRUE)

Arguments

Value

Invisibly returns file. This function is called for its side effects.

Writing Scalars

By default, h5_write saves single-element vectors as 1-dimensional arrays. To write a true HDF5 scalar, wrap the value in I() to treat it "as-is."

Examples

h5_write(I(5), file, "x") # Creates a scalar dataset
h5_write(5, file, "x")    # Creates a 1D array of length 1

Data Type Selection (as Argument)

By default, as = "auto" will automatically select the most appropriate data type for the given object. For numeric types, this will be the smallest type that can represent all values in the vector. For character types, h5lite will use a ragged vs rectangular heuristic, favoring small file size over fast I/O. For R data types not mentioned below, see vignette("data-types") for information on their fixed mappings to HDF5 data types.

Numeric and Logical Vectors

When writing a numeric or logical vector, you can specify one of the following storage types for it:

• Floating Point: "float16", "float32", "float64", "bfloat16"

• Signed Integer: "int8", "int16", "int32", "int64"

• Unsigned Integer: "uint8", "uint16", "uint32", "uint64"

NOTE: NA values must be stored as float64. NaN, Inf, and -Inf must be stored as a floating point type.

Examples

h5_write(1:100, file, "big_ints", as = "int64")
h5_write(TRUE,  file, "my_bool",  as = "float32")

Character Vectors

You can control whether character vectors are stored as variable or fixed length strings, and whether to use UTF-8 or ASCII encoding.

• Variable Length Strings: "utf8", "ascii"

• Fixed Length Strings:

  • "utf8[]" or "ascii[]" (length is set to the longest string)

  • "utf8[n]" or "ascii[n]" (where n is the length in bytes)

NOTE: Variable-length strings allow for NA values but cannot be compressed on disk. Fixed-length strings allow for compression but do not support NA.

Examples

h5_write(letters[1:5],    file, "len10_strs", as = "utf8[10]")
h5_write(c('X', 'Y', NA), file, "var_chars",  as = "ascii")

Lists, Data Frames, and Attributes

Provide a named vector to apply type mappings to sub-components of data. Set "skip" as the type to skip a specific component.

• Specific Name: "col_name" = "type" (e.g., c(score = "float32"))

• Specific Attribute: "@attr_name" = "type"

• Class-based: ".integer" = "type", ".numeric" = "type"

• Class-based Attribute: "@.character" = "type", "@.logical" = "type"

• Global Fallback: "." = "type"

• Global Attribute Fallback: "@." = "type"

Examples

# To strip attributes when writing:
h5_write(data, file, 'no_attrs_obj', as = c('@.' = "skip"))

# To only save the `hp` and `wt` columns:
h5_write(mtcars, file, 'my_df', as = c('hp' = "auto", 'wt' = "float32", '.' = "skip"))

Dimension Scales

h5lite automatically writes names, row.names, and dimnames as HDF5 dimension scales. Named vectors will generate an ⁠<name>_names⁠ dataset. A data.frame with row names will generate an ⁠<name>_rownames⁠ dataset (column names are saved internally in the original dataset). Matrices will generate ⁠<name>_rownames⁠ and ⁠<name>_colnames⁠ datasets. Arrays will generate ⁠<name>_dimscale_1⁠, ⁠<name>_dimscale_2⁠, etc. Special HDF5 metadata attributes link the dimension scales to the dataset. The dimension scales can be relocated with h5_move() without breaking the link.

See Also

h5_read()

Examples

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

# 1. Writing Basic Datasets
h5_write(1:10, file, "data/integers")
h5_write(rnorm(10), file, "data/floats")
h5_write(letters[1:5], file, "data/chars")

# 2. Writing Attributes
# Write an object first
h5_write(1:10, file, "data/vector")
# Attach an attribute to it using the 'attr' parameter
h5_write(I("My Description"), file, "data/vector", attr = "description")
h5_write(I(100), file, "data/vector", attr = "scale_factor")

# 3. Controlling Data Types
# Store values as 32-bit signed integers
h5_write(1:5, file, "small_ints", as = "int32")

# 4. Writing Complex Structures (Lists/Groups)
my_list <- list(
  meta    = list(id = 1, name = "Experiment A"),
  results = matrix(runif(9), 3, 3),
  valid   = I(TRUE)
)
h5_write(my_list, file, "experiment_1", as = c(id = "uint16"))

# 5. Writing Data Frames (Compound Datasets)
df <- data.frame(
  id    = 1:5,
  score = c(10.5, 9.2, 8.4, 7.1, 6.0),
  grade = factor(c("A", "A", "B", "C", "D"))
)
h5_write(df, file, "records/scores", as = c(grade = "ascii[1]"))

# 6. Fixed-Length Strings
h5_write(c("A", "B"), file, "fixed_str", as = "ascii[10]")

# 7. Review the file structure
h5_str(file)

# 8. Clean up
unlink(file)