How do I compute the second derivative of an one dimensional array in C#? has anyone done this before ?

CodePudding user response：

You can declare an extension method that returns pairs of sequential numbers:

public static IEnumerable<(T Previous, T Next)> PreviousAndNext<T>(this IEnumerable<T> self)
{
    using (var iter = self.GetEnumerator())
    {
        if (!iter.MoveNext())
            yield break;
        var previous = iter.Current;
        while (iter.MoveNext())
        {
            var next = iter.Current;
            yield return (previous, next);
            previous = next;
        }
    }
}

If you want the discrete derivative, i.e. difference between sequential numbers you would do: myArray.PreviousAndNext().Select((p, n) => n-p). If you want the second discrete derivative you would just repeat the function, i.e.

myArray.PreviousAndNext().Select((p, n) => n-p)
       .PreviousAndNext().Select((p, n) => n-p);

You could repeat this pattern however many times you want.