Calculate difference from previous item with LINQ

Question

I\'m trying to prepare data for a graph using LINQ.

The problem that i cant solve is how to calculate the \"difference to previous.

the result I expect is <

Answer 1

Yet another mod on Jon Skeet's version (thanks for your solution +1). Except this is returning an enumerable of tuples.

public static IEnumerable<Tuple<T, T>> Intermediate<T>(this IEnumerable<T> source)
{
    using (var iterator = source.GetEnumerator())
    {
        if (!iterator.MoveNext())
        {
            yield break;
        }
        T previous = iterator.Current;
        while (iterator.MoveNext())
        {
            yield return new Tuple<T, T>(previous, iterator.Current);
            previous = iterator.Current;
        }
    }
}

This is NOT returning the first because it's about returning the intermediate between items.

use it like:

public class MyObject
{
    public int ID { get; set; }
    public DateTime Date { get; set; }
    public int Value { get; set; }
}

var myObjectList = new List<MyObject>();

// don't forget to order on `Date`

foreach(var deltaItem in myObjectList.Intermediate())
{
    var delta = deltaItem.Second.Offset - deltaItem.First.Offset;
    // ..
}

OR

var newList = myObjectList.Intermediate().Select(item => item.Second.Date - item.First.Date);

OR (like jon shows)

var newList = myObjectList.Intermediate().Select(item => new 
{ 
    ID = item.Second.ID, 
    Date = item.Second.Date, 
    DateDiff = (item.Second.Date - item.First.Date).Days
});