/// <summary>
/// Returns the largest value of the <paramref name="ndArray"/>.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="ndArray"></param>
/// <returns></returns>
public static T Max <T>(this INdArray <T> ndArray)
{
var len = ndArray.Shape.TotalLength;
Guard.AssertOperation(len > 0, "ndArray has no elements.");
var max = ndArray.GetItem(0);
for (var i = 1; i < len; ++i)
{
var current = ndArray.GetItem(i);
if (ValueTrait.GreaterThan(current, max))
{
max = current;
}
}
return(max);
}
/// <summary>
/// Computes sum from all elements of the <paramref name="ndArray"/>.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="ndArray"></param>
/// <returns></returns>
public static T Sum <T>(this INdArray <T> ndArray)
{
var value = ValueTrait.Zero <T>();
var len = ndArray.Shape.TotalLength;
for (var i = 0; i < len; ++i)
{
value = ValueTrait.Add(value, ndArray.GetItem(i));
}
return(value);
}
/// <summary>
/// Returns the index of the smallest value of the <paramref name="ndArray"/>.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="ndArray"></param>
/// <returns></returns>
public static IndexArray ArgMin <T>(this INdArray <T> ndArray)
{
var len = ndArray.Shape.TotalLength;
Guard.AssertOperation(len > 0, "ndArray has no elements.");
var argmin = 0;
var min = ndArray.GetItem(0);
for (var i = 1; i < len; ++i)
{
var current = ndArray.GetItem(i);
if (ValueTrait.LessThan(current, min))
{
argmin = i;
min = current;
}
}
return(ndArray.ToShapedIndices(argmin));
}
/// <summary>
/// Computes unbiased variance from all elements of the <paramref name="ndArray"/>.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="ndArray"></param>
/// <returns></returns>
public static T UnbiasedVar <T>(this INdArray <T> ndArray)
{
var value = ValueTrait.Zero <T>();
var mean = ndArray.Mean();
var len = ndArray.Shape.TotalLength;
for (var i = 0; i < len; ++i)
{
var temp = ValueTrait.Subtract(ndArray.GetItem(i), mean);
value = ValueTrait.Multiply(temp, temp);
}
return(ValueTrait.Divide(value, ValueTrait.FromLong <T>(len - 1)));
}
/// <summary>
/// [Pure] Returns the 2-D norm of all elements of <paramref name="ndArray"/>.
/// </summary>
/// <param name="ndArray"></param>
/// <returns></returns>
public static T Norm2 <T>(this INdArray <T> ndArray)
{
var len = ndArray.Shape.TotalLength;
Guard.AssertOperation(len > 0, "ndArray has no elements.");
var norm = ValueTrait.Zero <T>();
for (var i = 0; i < len; ++i)
{
var element = ndArray.GetItem(i);
norm = ValueTrait.Add(norm, ValueTrait.Multiply(element, element));
}
return(NdMath.Sqrt(norm));
}
