Question

Good Evening everyone,

I’ve been trying to figure out the most efficient way to do this, but am falling short. Here’s how it goes…

I am ultimately trying to determine “like customers” based on a specific customer’s buying habits and a given threshold, say 50%. IE customer 1 purchased products A,B,C,D … customer 2 purchased B,C,D,E … these two customers are >= 50% “likeness” so they should be matched.

My schema is as would be expected

CLIENT (1 ----- many)  CLIENT_PURCHASE (1 -------many) PRODUCT

*clientID            *clientID *prodID                 *prodID

For now I am ignoring the threshold and simply am trying to find customers who have purchased any item within customer 1’s history. I think I have this working with the following two queries:

var clientOneHistory = (from cp in client.Client_Purchase
                        select cp.prodID).ToList();

var matchedClients = (from cp in db.Client_Purchase
                        where clientOneHistory.Contains(cp.prodID)
                        select cp.Client.fullname).Distinct().ToList();

So my ultimate question is, “How do I work in the threshold portion?”
Thanks for your time

Answer 1

I’m not sure exactly how to form these queries for your particular case. Assuming you want to use LINQ-to-SQL. Instead, I’ll use the NorthWind database as an example to do the same thing. You could then use the ideas used here in your implementation. I don’t think it’s possible to do this completely using LINQ-to-SQL, you’ll have to do a mix.

var threshold = 0.5M;

// let's pick a customer id
var myId = "VINET";

// get products of current customer
var myProducts = (from c in db.Customers
                  where c.CustomerID == myId
                  join o in db.Orders on c.CustomerID equals o.CustomerID
                  join od in db.Order_Details on o.OrderID equals od.OrderID
                  select od.ProductID)
                 .Distinct()
                 .ToArray();

// get the products of all other customers
var others = (from c in db.Customers
              where c.CustomerID != myId
              join o in db.Orders on c.CustomerID equals o.CustomerID
              join od in db.Order_Details on o.OrderID equals od.OrderID
              group od.ProductID by c.CustomerID into g
              select new { CustomerID = g.Key, Products = g.Distinct() })
             .AsEnumerable();

// calculate "likeness" values for each person
var likeness = from o in others
               let Percent = Decimal.Divide(myProducts.Intersect(o.Products).Count(), myProducts.Length)
               where Percent >= threshold
               select new { o.CustomerID, Percent };