IVector _Derivative(IVector th, float lambda)
{
using (var p0 = _feature.Multiply(th))
using (var p1 = p0.Column(0))
using (var p = p1.Sigmoid())
using (var e0 = p.Subtract(_target))
using (var e = e0.ToRowMatrix())
using (var e2 = e.Multiply(_feature)) {
e2.Multiply(1f / _feature.RowCount);
var ret = e2.Row(0);
if (lambda != 0)
{
using (var reg = _lap.CreateIndexable(th.Count))
using (var thi = th.AsIndexable()) {
var term = lambda / _feature.RowCount;
for (var i = 1; i < th.Count; i++)
{
reg[i] = thi[i] * term;
}
using (var reg2 = _lap.Create(reg))
ret.Add(reg2);
}
}
return(ret);
}
}
public IIndexableVector CreateIndexable(int length)
{
return(_numerics.CreateIndexable(length));
}