Combining multiple sequences into 1 object

Question

What is the correct way to iterate through several sequences/list etc., and combine them respectively in an object. For example, I have a list of teams, and two different lists of stats. I would like to combine the two list of stats with the respective team in the list of teams and that to a class. Hope this makes since. Thanks in advance.

Vulpes · Answer

Assuming that the sequences are already in the correct order then something like this is probably easiest and should scale OK to more that 3 sequences: using System; using System.Collections.Generic; using System.Linq; class Team { public string Name {get; set;} public int Stat1 {get; set;} public int Stat2 {get; set;} public Team(string name int stat1 int stat2) { Name = name; Stat1 = stat1; Stat2 = stat2; } public override string ToString() { return String.Format(Name = {0} Stat1 = {1} Stat2 = {2} Name Stat1 Stat2); } } class Program { static void Main() { List teams = new List {team1 team2 team3}; List stats1 = new List {100 90 80}; List stats2 = new List {85 75 95}; List teamList = teams.Select((t i) => new Team(t stats1[i] stats2[i])).ToList(); foreach(Team team in teamList) Console.WriteLine(team); Console.ReadKey(); } }

Vulpes · Answer

To convert the negative values into positive values all you need to do is to use the absolute value of the difference in scores: Spread = g.Average(at => (decimal)Math.Abs(at.awayScore - at.homeScore))

Vulpes · Answer

TBH Rich it doesn't make complete sense because what you've called a Season seems to me to be a Game and in any case a Season class can't have a property of the same name. Also I'd have thought that your AwayRecord class needs an additional property for the name of the team (Team say) and I wasn't clear what the date property was storing unless it's the date of the first away game for that team. Anyway for now I've ignored the Season and date properties and just populated the others with this query which as you suspected requires the GroupBy extension method: List awayRecords = this.NBAGetSeasonScores(). GroupBy(s => s.awayTeam).OrderBy(g => g.Key).Select(g => new AwayRecord{Team = g.Key Wins = g.Count(s => s.awayScore > s.homeScore) Losses = g.Count(s => s.awayScore

Vulpes · Answer

Off the top of my head I'd say: List GoalPercent = off.Select( o => new GoalPercent(o.Team (decimal)o.FGM/o.FGA * 100m) ).ToList();

Vulpes · Answer

In your first query: List teams = this.NBAgetTeams().AsEnumerable().OrderBy(t => t.Abreviated_Long).Select(t => t).ToList(); you could omit the Select() method which isn't actually doing anything: List teams = this.NBAgetTeams().AsEnumerable().OrderBy(t => t.Abreviated_Long).ToList(); but other than that it's fine. I woudn't try to cram too much into your LINQ queries as it makes them harder to understand and to maintain. I thought these seemed just right :)

Rich · Answer

Vulpes the following code works for me perfectly but I am wondering if there is a more concise or efficient way of obtaining the desired results. public List NBAgetStandings() { List teams = this.NBAgetTeams().AsEnumerable().OrderBy(t => t.Abreviated_Long) .Select(t => t).ToList(); List AwayRecord = this.NBAGetSeasonScores().GroupBy(ar => ar.away) .OrderBy(t => t.Key).Select(t => new NBAstandings { Teams = t.Key Wins = t.Count(at => at.awayScore > at.homeScore) Losses = t.Count(at => at.awayScore Spread = t.Sum(at => Math.Abs((decimal)at.awayScore - (decimal)at.homeScore)) Total = t.Sum(at => (decimal)at.awayScore + (decimal)at.homeScore) }).AsEnumerable().ToList(); List HomeRecord = this.NBAGetSeasonScores().GroupBy(hr => hr.home) .OrderBy(t => t.Key).Select(t => new NBAstandings { Teams = t.Key Wins = t.Count(ht => ht.homeScore > ht.awayScore) Losses = t.Count(ht => ht.homeScore Spread = t.Sum(ht => Math.Abs((decimal)ht.homeScore - (decimal)ht.awayScore)) Total = t.Sum(ht => (decimal)ht.homeScore + (decimal)ht.awayScore) }).AsEnumerable().ToList(); List TotalSeason = teams.Select((t i) => new NBAstandings (t.Abreviated_Long AwayRecord[i] HomeRecord[i])).ToList(); return TotalSeason; } public class NBAstandings { public string Teams { get; set; } public int Wins { get; set; } public int Losses { get; set; } public decimal Spread { get; set; } public decimal Total { get; set; } public NBAstandings AR { get; set; } public NBAstandings HR { get; set; } // Constructors public NBAstandings() {} public NBAstandings(string teams NBAstandings ar NBAstandings hr) { Teams = teams; Wins = ar.Wins + hr.Wins; Losses = ar.Losses + hr.Losses; Spread = (ar.Spread + hr.Spread)/(ar.Wins + hr.Wins + ar.Losses + hr.Losses); Total = (ar.Total + hr.Total)/(ar.Wins + hr.Wins + ar.Losses + hr.Losses); } } }

Vulpes · Answer

I have a number of ideas for future articles but unfortunately I don't have the time to write them just now :( A problem with writing an article about something like this is that you need to have a basic grasp of LINQ in order to be able to understand it and I'm not sure that many C# developers do. Anyway thanks for the idea and I'll add it to the list :)

Rich · Answer

Vulpes have you thought about writing an article on these type of LINQ scenarios? Particularly on LINQ extension methods involving calculations based on properties from different sequences objects etc. I've searched the web and can only fine basic LINQ examples to learn from but nothing as specific as what you have taught me thus far. I think a lot of new programmers such as myself would really benefit from such an article.

Vulpes · Answer

Don't understand that as (at.awayScore - at.homeScore) is integral and Math.Abs has an overload for Int32 as well as Decimal. Might be a LINQ to SQL peculiarity but no matter if it's OK working for you :)

Rich · Answer

worked perfectly but for some reason I had to move the casting though: Spread = g.Average(at => Math.Abs((decimal)at.awayScore - (decimal)at.homeScore))

Rich · Answer

Vulpes your query worked like a charm. I have yet created another challenge for myself. I added two more properties to the AwayRecord class which are Spread and Total. The Spread property should hold the average point amount an away team wins or looses by(awayScore - homeScore) while the Total property should hold the average point total of the game(awayScore + homeScore). The Total property was easy enough but I am having trouble trying to figure out how to correctly query for the Spread property since the away team isn't always a winner therefore producing unwanted negative results( awayScore 80 - homeScore 100). I am guessing this may involve a nested lambda expression and possibly creating another class. Here is what I have so far: // Get NBA Away Record public List NBAteamAwayRecord() { List AwayRecord = this.NBAGetSeasonScores().GroupBy(at => at.away) .OrderBy(g => g.Key).Select(g => new NBAawayRecord { Teams = g.Key Wins = g.Count(at => at.awayScore > at.homeScore)  Losses = g.Count(at => at.awayScore  Spread = g.Average(?????)  Total = g.Average(at => (decimal)at.awayScore + (decimal)at.homeScore) }).AsEnumerable().ToList(); return AwayRecord; }

Rich · Answer

Vulpes yeah thanks for pointing out those errors. I went back and made updates to the post. Season would be the year such as 1980. The date property represents the date of the game played. Your example makes since and I think it should work. I'll try to implement it shortly and let you know the result. I really appreciate your insight and time. As a new programmer it helps me out to see real world examples of the language in action.

Rich · Answer

Vulpes I have yet another problem that I am having trouble with. I have this class: public class NBASeason { public int Season {get;set;} public datetime date {get;set;} public string awayTeam {get;set;} public int awayScore {get;set;} public string homeTeam {get;set;} public int homeScore {get;set;} } I basically want to calculate each away team's win/loss record and place it in another class such as: class AwayRecord { public string AwayTeam {get;set;} public int Wins {get;set} public int Losses {get;set} } I have already made a list that queried the winning away teams: List Season > w = this .NBAGetSeasonScores().Where(atw => atw.awayScore > atw.homeScore) .OrderBy(away => away.away).AsEnumerable().ToList(); From this point I suspect a lambda GroupBy extension method may be needed as the awayTeam property in the Season class will contain several copies of the same team but I have yet to correctly figure this out. Hope this makes since. Thanks in advance.

Vulpes · Answer

Afraid not Rich. The only 'tweeting' I do is on here :)

Rich · Answer

That did it thanks! I really appreciate your help. Do you have a twitter account that I can follow?

Rich · Answer

Vulpes I have another related question. I am now trying to figure out how to perform calculations on a list of objects and then put the results in a new list. for example: List off = new List { new OffenseStats {Team= Bears FGA = 50 FGM = 25} new OffenseStats {Team= Lions FGA = 70 FGM = 20} }; How can I then create the equation FGM/FGA for each team and then put the results in a new List: List GoalPercent = ????? The GoalPercent class would look something like this: class GoalPercent() { public string Team {get; set;} decimal GoalPercent {get; set;} public GoalPercent(string team decimal gp) { Team = team; GoalPercent = gp; } } Thanks in advance.

Rich · Answer

Vulpes thanks! Your answer helped me out and I have a much better understanding of the lambda expression.

Vulpes · Answer

't' represents each string in the 'teams' list and 'i' represents its index in that list. So for the first element 't' will team1 and 'i' will be 0. We can then use 'i' to read off the stats for a particular team from the other 2 lists.

Rich · Answer

Vulpes thanks for the response. I will try this out shortly but as I am new to programming I have a question about the lamda expression associated with the list teamList. What do the parameters t and i represent in teams.Select((t i) => new Team(t stats1[i] stats2[i])).ToList(); ?