/// <summary>
/// Calculates the difference between adjoining elements along the specified axes.
/// </summary>
/// <param name="axis">The axis to operate along.</param>
/// <param name="source">The NdArray containing the source values.</param>
/// <returns>The differences NdArray. It has one element less in dimension <paramref name="axis"/> as the source NdArray.</returns>
public static NdArray <T> DiffAxis(int axis, NdArray <T> source)
{
NdArray <T> .CheckAxis(axis, source);
var shiftRanges = new List <IRange>();
var cutRanges = new List <IRange>();
for (var index = 0; index < source.NumDimensions; index++)
{
if (index == axis)
{
shiftRanges.Add(RangeFactory.Range(1, SpecialIdx.None));
cutRanges.Add(RangeFactory.Range(SpecialIdx.None, source.Shape[index] - 2));
}
else
{
shiftRanges.Add(RangeFactory.All);
cutRanges.Add(RangeFactory.All);
}
}
var shiftArray = source[shiftRanges.ToArray()];
var cutArray = source[cutRanges.ToArray()];
return(shiftArray - cutArray);
}
/// <summary
/// >Creates a NdArray with the specified diagonal along the given axes.
/// </summary>
/// <param name="axis1">The first dimension of the diagonal.</param>
/// <param name="axis2">The seconds dimension of the diagonal.</param>
/// <param name="source">The values for the diagonal.</param>
/// <returns>A NdArray having the values <paramref name="a"/> on the diagonal specified by the axes
public static NdArray <T> DiagMatAxis(int axis1, int axis2, NdArray <T> source)
{
if (axis1 == axis2)
{
var errorMessage = string.Format("axes [axis1={0}, axis2={1}] to use for diagonal must be different", axis1, axis2);
throw new ArgumentException(errorMessage, "axis2");
}
var ax1 = axis1 < axis2 ? axis1 : axis2;
var ax2 = axis1 < axis2 ? axis2 : axis1;
NdArray <T> .CheckAxis(ax1, source);
if (!(ax2 >= 0 && ax2 <= source.NumDimensions))
{
var errorMessage = string.Format("Cannot insert axis at position {0} into array of shape {1}.", ax2, ErrorMessage.ShapeToString(source.Shape));
throw new ArgumentException(errorMessage, "axis2");
}
var shape = List.Insert(ax2, source.Shape[ax1], source.Shape);
var result = NdArray <T> .Zeros(source.Storage.Device, shape);
var diag = DiagAxis(ax1, ax2, result);
FillFrom(diag, source);
return(result);
}
/// <summary>
/// Repeats the NdArray along an axis.
/// </summary>
/// <param name="axis">The axis to repeat along.</param>
/// <param name="repeats">The number of repetitions.</param>
/// <param name="source">The NdArray to repeat.</param>
/// <returns>The repeated NdArray.</returns>
public static NdArray <T> Replicate(int axis, int repeats, NdArray <T> source)
{
NdArray <T> .CheckAxis(axis, source);
if (repeats < 0)
{
throw new ArgumentException("Number of repetitions cannot be negative.", "repeats");
}
// 1. insert axis of size one left to repetition axis
// 2. broadcast along the new axis to number of repetitions
// 3. reshape to result shape
var step1 = source.Reshape(List.Insert(axis, 1, source.Shape));
var step2 = NdArray <T> .BraodcastDim(axis, repeats, step1);
var step3 = step2.Reshape(List.Set(axis, repeats * source.Shape[axis], source.Shape));
return(step3);
}
