bdgetDiagonal_hdf5

bdgetDiagonal_hdf5

HDF5_ALGEBRA

1 Description

Retrieves the diagonal elements from a matrix stored in an HDF5 file.

2 Usage

bdgetDiagonal_hdf5(filename, group, dataset)

3 Arguments

Parameter	Description
`filename`	Character string. Path to the HDF5 file.
`group`	Character string. Path to the group containing the dataset.
`dataset`	Character string. Name of the dataset.

4 Value

Numeric vector containing diagonal elements.

5 Details

This function provides efficient access to matrix diagonal elements with: - Access features: - Direct diagonal access - Memory-efficient retrieval - Support for large matrices - Implementation features: - Safe HDF5 file operations - Memory-efficient implementation - Comprehensive error handling - Read-only access to files

The function opens the HDF5 file in read-only mode to ensure data safety.

6 Examples

Code

library(BigDataStatMeth)

# Create test matrix
X <- matrix(rnorm(100), 10, 10)
diag(X) <- 0.5

# Save to HDF5
bdCreate_hdf5_matrix("test.hdf5", X, "data", "matrix1",
                     overwriteFile = TRUE)

# Get diagonal
diag_elements <- bdgetDiagonal_hdf5("test.hdf5", "data", "matrix1")
print(diag_elements)

# Cleanup
if (file.exists("test.hdf5")) {
  file.remove("test.hdf5")
}

7 See Also

bdWriteDiagonal_hdf5 for writing diagonal elements
bdCreate_hdf5_matrix for creating HDF5 matrices

---
title: "bdgetDiagonal_hdf5"
subtitle: "bdgetDiagonal_hdf5"
---

<span class="category-badge hdf5_algebra">HDF5_ALGEBRA</span>

## Description

Retrieves the diagonal elements from a matrix stored in an HDF5 file.

## Usage

```r
bdgetDiagonal_hdf5(filename, group, dataset)
```
## Arguments

::: {.param-table}
| Parameter | Description |
|-----------|-------------|
| `filename` | Character string. Path to the HDF5 file. |
| `group` | Character string. Path to the group containing the dataset. |
| `dataset` | Character string. Name of the dataset.  |
:::

## Value

::: {.return-value}
Numeric vector containing diagonal elements.

:::
## Details

This function provides efficient access to matrix diagonal elements with:
- Access features:
  - Direct diagonal access
  - Memory-efficient retrieval
  - Support for large matrices
- Implementation features:
  - Safe HDF5 file operations
  - Memory-efficient implementation
  - Comprehensive error handling
  - Read-only access to files

The function opens the HDF5 file in read-only mode to ensure data safety.


## Examples

```{r}
#| eval: false
#| code-fold: show

library(BigDataStatMeth)

# Create test matrix
X <- matrix(rnorm(100), 10, 10)
diag(X) <- 0.5

# Save to HDF5
bdCreate_hdf5_matrix("test.hdf5", X, "data", "matrix1",
                     overwriteFile = TRUE)

# Get diagonal
diag_elements <- bdgetDiagonal_hdf5("test.hdf5", "data", "matrix1")
print(diag_elements)

# Cleanup
if (file.exists("test.hdf5")) {
  file.remove("test.hdf5")
}
```

## See Also

::: {.see-also}
- [bdWriteDiagonal_hdf5](bdWriteDiagonal_hdf5.html) for writing diagonal elements
- [bdCreate_hdf5_matrix](../hdf5_io_management/bdCreate_hdf5_matrix.html) for creating HDF5 matrices

:::