NDIndex (Deep Java Library 0.11.0 API specification)

java.lang.Object
- ai.djl.ndarray.index.NDIndex

```
public class NDIndex
extends java.lang.Object
```
The NDIndex allows you to specify a subset of an NDArray that can be used for fetching or updating.
It accepts a different index option for each dimension, given in the order of the dimensions. Each dimension has options corresponding to:
- Return all dimensions - Pass null to addIndices
- A single value in the dimension - Pass the value to addIndices with a negative index -i corresponding to [dimensionLength - i]
- A range of values - Use addSliceDim
We recommend creating the NDIndex using NDIndex(String, Object...).
See Also:

NDIndex(String, Object...)

Constructor Summary

Constructors
Constructor and Description
`NDIndex()` Creates an empty `NDIndex` to append values to.
`NDIndex(long... indices)` Creates an NDIndex with the given indices as specified values on the NDArray.
`NDIndex(java.lang.String indices, java.lang.Object... args)` Creates a `NDIndex` given the index values.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`NDIndex`	`addAllDim()` Appends a new index to get all values in the dimension.
`NDIndex`	`addAllDim(int count)` Appends multiple new index to get all values in the dimension.
`NDIndex`	`addBooleanIndex(NDArray index)` Updates the NDIndex by appending a boolean NDArray.
`NDIndex`	`addIndices(long... indices)` Updates the NDIndex by appending indices as specified values on the NDArray.
`NDIndex`	`addIndices(java.lang.String indices, java.lang.Object... args)` Updates the NDIndex by appending indices to the array.
`NDIndex`	`addPickDim(NDArray index)` Appends a picking index that gets values by index in the axis.
`NDIndex`	`addSliceDim(long min, long max)` Appends a new index to slice the dimension and returns a range of values.
`NDIndex`	`addSliceDim(long min, long max, long step)` Appends a new index to slice the dimension and returns a range of values.
`NDIndexElement`	`get(int dimension)` Returns the index affecting the given dimension.
`int`	`getEllipsisIndex()` Returns the index of the ellipsis.
`java.util.List<NDIndexElement>`	`getIndices()` Returns the indices.
`int`	`getRank()` Returns the number of dimensions specified in the Index.
`static NDIndex`	`sliceAxis(int axis, long min, long max)` Creates an `NDIndex` that just has one slice in the given axis.
`java.util.stream.Stream<NDIndexElement>`	`stream()` Returns a stream of the NDIndexElements.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - NDIndex
```
public NDIndex()
```
    Creates an empty NDIndex to append values to.
  - NDIndex
```
public NDIndex(java.lang.String indices,
               java.lang.Object... args)
```
    Creates a NDIndex given the index values.
    Here are some examples of the indices format.
```
     NDArray a = manager.ones(new Shape(5, 4, 3));

     // Gets a subsection of the NDArray in the first axis.
     assertEquals(a.get(new NDIndex("2")).getShape(), new Shape(4, 3));

     // Gets a subsection of the NDArray indexing from the end (-i == length - i).
     assertEquals(a.get(new NDIndex("-1")).getShape(), new Shape(4, 3));

     // Gets everything in the first axis and a subsection in the second axis.
     // You can use either : or * to represent everything
     assertEquals(a.get(new NDIndex(":, 2")).getShape(), new Shape(5, 3));
     assertEquals(a.get(new NDIndex("*, 2")).getShape(), new Shape(5, 3));

     // Gets a range of values along the second axis that is inclusive on the bottom and exclusive on the top.
     assertEquals(a.get(new NDIndex(":, 1:3")).getShape(), new Shape(5, 2, 3));

     // Excludes either the min or the max of the range to go all the way to the beginning or end.
     assertEquals(a.get(new NDIndex(":, :3")).getShape(), new Shape(5, 3, 3));
     assertEquals(a.get(new NDIndex(":, 1:")).getShape(), new Shape(5, 4, 3));

     // Uses the value after the second colon in a slicing range, the step, to get every other result.
     assertEquals(a.get(new NDIndex(":, 1::2")).getShape(), new Shape(5, 2, 3));

     // Uses a negative step to reverse along the dimension.
     assertEquals(a.get(new NDIndex("-1")).getShape(), new Shape(5, 4, 3));

     // Uses a variable argument to the index
     // It can replace any number in any of these formats with {} and then the value of {}
     // is specified in an argument following the indices string.
     assertEquals(a.get(new NDIndex("{}, {}:{}", 0, 1, 3)).getShape(), new Shape(2, 3));

     // Uses ellipsis to insert many full slices
     assertEquals(a.get(new NDIndex("...")).getShape(), new Shape(5, 4, 3));

     // Uses ellipsis to select all the dimensions except for last axis where we only get a subsection.
     assertEquals(a.get(new NDIndex("..., 2")).getShape(), new Shape(5, 4));
 
```
    Parameters:
    
    indices - a comma separated list of indices corresponding to either subsections, everything, or slices on a particular dimension
    
    args - arguments to replace the variable "{}" in the indices string. Can be an integer, long, boolean NDArray, or integer NDArray.
    
    See Also:
    
    Numpy Indexing
  - NDIndex
```
public NDIndex(long... indices)
```
    Creates an NDIndex with the given indices as specified values on the NDArray.
    
    Parameters:
    
    indices - the indices with each index corresponding to the dimensions and negative indices starting from the end
- Method Detail
  - sliceAxis
```
public static NDIndex sliceAxis(int axis,
                                long min,
                                long max)
```
    Creates an NDIndex that just has one slice in the given axis.
    
    Parameters:
    
    axis - the axis to slice
    
    min - the min of the slice
    
    max - the max of the slice
    
    Returns:
    
    a new NDIndex with the given slice.
  - getRank
```
public int getRank()
```
    Returns the number of dimensions specified in the Index.
    
    Returns:
    
    the number of dimensions specified in the Index
  - getEllipsisIndex
```
public int getEllipsisIndex()
```
    Returns the index of the ellipsis.
    
    Returns:
    
    the index of the ellipsis within this index or -1 for none.
  - get
```
public NDIndexElement get(int dimension)
```
    Returns the index affecting the given dimension.
    
    Parameters:
    
    dimension - the affected dimension
    
    Returns:
    
    the index affecting the given dimension
  - getIndices
```
public java.util.List<NDIndexElement> getIndices()
```
    Returns the indices.
    
    Returns:
    
    the indices
  - addIndices
```
public final NDIndex addIndices(java.lang.String indices,
                                java.lang.Object... args)
```
    Updates the NDIndex by appending indices to the array.
    
    Parameters:
    
    indices - the indices to add similar to NDIndex(String, Object...)
    
    args - arguments to replace the variable "{}" in the indices string. Can be an integer, long, boolean NDArray, or integer NDArray.
    
    Returns:
    
    the updated NDIndex
    
    See Also:
    
    NDIndex(String, Object...)
  - addIndices
```
public final NDIndex addIndices(long... indices)
```
    Updates the NDIndex by appending indices as specified values on the NDArray.
    
    Parameters:
    
    indices - with each index corresponding to the dimensions and negative indices starting from the end
    
    Returns:
    
    the updated NDIndex
  - addBooleanIndex
```
public NDIndex addBooleanIndex(NDArray index)
```
    Updates the NDIndex by appending a boolean NDArray.
    The NDArray should have a matching shape to the dimensions being fetched and will return where the values in NDIndex do not equal zero.
    
    Parameters:
    
    index - a boolean NDArray where all nonzero elements correspond to elements to return
    
    Returns:
    
    the updated NDIndex
  - addAllDim
```
public NDIndex addAllDim()
```
    Appends a new index to get all values in the dimension.
    
    Returns:
    
    the updated NDIndex
  - addAllDim
```
public NDIndex addAllDim(int count)
```
    Appends multiple new index to get all values in the dimension.
    
    Parameters:
    
    count - how many axes of NDIndexAll to add.
    
    Returns:
    
    the updated NDIndex
    
    Throws:
    
    java.lang.IllegalArgumentException - if count is negative
  - addSliceDim
```
public NDIndex addSliceDim(long min,
                           long max)
```
    Appends a new index to slice the dimension and returns a range of values.
    
    Parameters:
    
    min - the minimum of the range
    
    max - the maximum of the range
    
    Returns:
    
    the updated NDIndex
  - addSliceDim
```
public NDIndex addSliceDim(long min,
                           long max,
                           long step)
```
    Appends a new index to slice the dimension and returns a range of values.
    
    Parameters:
    
    min - the minimum of the range
    
    max - the maximum of the range
    
    step - the step of the slice
    
    Returns:
    
    the updated NDIndex
  - addPickDim
```
public NDIndex addPickDim(NDArray index)
```
    Appends a picking index that gets values by index in the axis.
    
    Parameters:
    
    index - the indices should be NDArray. For each element in the indices array, it acts like a fixed index returning an element of that shape. So, the final shape would be indices.getShape().addAll(target.getShape().slice(1)) (assuming it is the first index element).
    
    Returns:
    
    the updated NDIndex
  - stream
```
public java.util.stream.Stream<NDIndexElement> stream()
```
    Returns a stream of the NDIndexElements.
    
    Returns:
    
    a stream of the NDIndexElements

Class NDIndex

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

NDIndex

NDIndex

NDIndex

Method Detail

sliceAxis

getRank

getEllipsisIndex

get

getIndices

addIndices

addIndices

addBooleanIndex

addAllDim

addAllDim

addSliceDim

addSliceDim

addPickDim

stream