var newList = data.GroupBy(x => new { x.Symbol })
.Select
(
x =>
{
var subList = x.OrderBy(y => y.Date).ToList();
return subList.Select((y, idx) => new
{
Symbol = y.Symbol,
Close = y.Close,
Date = y.Date,
/*p = (idx < 1) ? null : subList.Skip(idx - 1)
.Take(2).Select(o => o.Close).ToList()*/,
Vol = (idx < 1) ? 0 : new DescriptiveStatistics
(subList.Skip(idx - 1).Take(2).Select(o => (double)o.Close/(double)
subList.ElementAt(idx - 1).Close).ToList()).StandardDeviation,
});
}
)
.SelectMany(x => x)
.ToList();
I want create a variable p = (idx < 1) ? null : subList.Skip(idx - 1).Take(2).Select(o => o.Close).ToList() with the same index idx of Vol but do not appear in the return just a temporary variable(but have to use the synchronous idx as Vol). So where to write down this p or how to change the syntax
You can hold a temp variable, just like you have done with subList although I dont have a test structure to build against something like this below should work.
var newList = data.GroupBy(x => new { x.Symbol })
.Select
(
x =>
{
var subList = x.OrderBy(y => y.Date).ToList();
return subList.Select((y, idx) => { //return is a function not an object
var p = (idx < 1) ? null : subList.Skip(idx - 1).Take(2).Select(o => o.Close).ToList(); //your p
return new //this return returns the object definition
{
Symbol = y.Symbol,
Close = y.Close,
Date = y.Date,
Vol = p == null ? 0 : new DescriptiveStatistics(subList.Skip(idx - 1).Take(2).Select(o => (double)o.Close / (double)subList.ElementAt(idx - 1).Close).ToList()).StandardDeviation,
};
});
}
)
.SelectMany(x => x)
.ToList();
Related
I have 2 almost identical linq queries and want to remove repeating code from it. The only difference is the extra property in the GroupBy depending on some true/false condition.
How can I conditionally group by in linq without repeating the code like below?
var allergensList = _context.RecipeAllergens
.Where(x => x.ParentId == Id && x.AllergenId != null)
.ToList();
var allergens = new List<AllergenInfo>();
if (isRecipe)
{
allergens = allergensList
.GroupBy(x => new { x.AllergenName, x.AllergenIcon, x.AllergenMaycontains })
.Select(a =>
{
var v = a.OrderBy(x => x.AllergenMaycontains).First();
return new AllergenInfo
{
AllergenName = v.AllergenName,
AllergenIcon = v.AllergenIcon,
AllergenMayContain = v.AllergenMaycontains ?? false
};
})
.ToList();
}
else
{
allergens = allergensList
.GroupBy(x => new { x.AllergenName, x.AllergenIcon })
.Select(a =>
{
var v = a.OrderBy(x => x.AllergenMaycontains).First();
return new AllergenInfo
{
AllergenName = v.AllergenName,
AllergenIcon = v.AllergenIcon,
AllergenMayContain = v.AllergenMaycontains ?? false
};
})
.ToList();
}
You can left grouping by x.AllergenMaycontains but under condition
allergens = allergensList
.GroupBy(x => new { x.AllergenName, x.AllergenIcon, AllergenMaycontains = isRecipe ? x.AllergenMaycontains : false })
.Select(a =>
{
var v = a.OrderBy(x => x.AllergenMaycontains).First();
return new AllergenInfo
{
AllergenName = v.AllergenName,
AllergenIcon = v.AllergenIcon,
AllergenMayContain = v.AllergenMaycontains ?? false
};
})
.ToList();
I want to use try-catch to check being divided by 0 in
((double)o.Close - (double)subList.Skip(idx - t + 1).First().Close) /
(double)subList.Skip(idx - t + 1).First().Close
...but I don't know where to add try-catch. I try to add including the whole var newList =, but it is not allowed, since variable newList no longer exists later. So where is the proper position to add try-catch?
var newList = data.GroupBy(o => o.Date).Where(o => o.Key <= Beginday).OrderByDescending(o => o.Key).Take(Y).SelectMany(o => o).GroupBy(x => new { x.Symbol })
.Select
(
x =>
{
var subList = x.OrderBy(y => y.Date).ToList();
return subList.Select((y, idx) =>
{
return new
{
Symbol = y.Symbol,
Close = y.Close,
Date = y.Date,
Vol = (idx < t - 1) ? 0 : new DescriptiveStatistics(subList.Skip(idx - t + 1).Take(t)
.Select(o =>
((double)o.Close - (double)subList.Skip(idx - t + 1).First().Close) / (double)subList.Skip(idx - t + 1).First().Close).ToList()).StandardDeviation,
};
});
}
)
.SelectMany(x => x)
.ToList();
depends on what you're going to do in your catch - if you want newList to have a valid value even if the divisor is 0 then you should probably have your 0 check integrated into the main code flow rather than using exceptional flows.
However, to directly answer your question as written, explicity declare newList to a default value first, then reassign within a try/catch block (place the entirety of the code you've written inside the try, with the explicit default declaration before the try). Then newList will exist when you need to use it later.
If you want to catch everything then
try
{
var newList = data.GroupBy(o => o.Date).Where(o => o.Key <= Beginday).OrderByDescending(o => o.Key).Take(Y).SelectMany(o => o).GroupBy(x => new { x.Symbol })
.Select
(
x =>
{
var subList = x.OrderBy(y => y.Date).ToList();
return subList.Select((y, idx) =>
{
return new
{
Symbol = y.Symbol,
Close = y.Close,
Date = y.Date,
Vol = (idx < t - 1) ? 0 : new DescriptiveStatistics(subList.Skip(idx - t + 1).Take(t)
.Select(o =>
((double)o.Close - (double)subList.Skip(idx - t + 1).First().Close) / (double)subList.Skip(idx - t + 1).First().Close).ToList()).StandardDeviation,
};
});
}
)
.SelectMany(x => x)
.ToList();
}
catch(Exception ex)
{
//your error
}
You can certainly do this:
var newList = new[]
{
new { Symbol = "", Close = 0.0, Date = DateTime.Now, Vol = 0 }
}.Take(0).ToList();
try
{
var newList = data.GroupBy(o => o.Date).Where(o => o.Key <= Beginday).OrderByDescending(o => o.Key).Take(Y).SelectMany(o => o).GroupBy(x => new { x.Symbol })
.Select
(
x =>
{
var subList = x.OrderBy(y => y.Date).ToList();
return subList.Select((y, idx) =>
{
return new
{
Symbol = y.Symbol,
Close = y.Close,
Date = y.Date,
Vol = (idx < t - 1) ? 0 : new DescriptiveStatistics(subList.Skip(idx - t + 1).Take(t)
.Select(o =>
((double)o.Close - (double)subList.Skip(idx - t + 1).First().Close) / (double)subList.Skip(idx - t + 1).First().Close).ToList()).StandardDeviation,
};
});
}
)
.SelectMany(x => x)
.ToList();
}
catch (Exception ex)
{
}
So long as the names and types are the same in the two anonymous types then this works fine.
I have List<string> {"", "1,5,4", "h", "5,8", "1"}. I need to divide into 3 List<int>. This is my code:
var parseString = condition.Trim().Split(separator).ToList();
var numberSections = new List<string>();
var numberRow = new List<string>();
var numberCell = new List<string>();
foreach (var str in parseString) {
if (int.TryParse(str.Substring(0, 1), out i) && numberSections.Count == 0) {
numberSections.Add(str);
parseString.Remove(str);
}
if (int.TryParse(str.Substring(0, 1), out i) && numberRow.Count == 0) {
numberRow.Add(str);
parseString.Remove(str);
}
if (int.TryParse(str.Substring(0, 1), out i) && numberCell.Count == 0) {
numberCell.Add(str);
parseString.Remove(str);
}
}
But it do not working. How I can do it?
Here is a LINQ version for it
var result = list.Select(x => x.Split(",".ToCharArray(),
StringSplitOptions.RemoveEmptyEntries)) // now we have List<List<string>>
.Select(x => x.Select(y =>
{
int value;
var isInt = int.TryParse(y, out value);
return isInt ? value : (int?)null;
})) // convert each element of inner list to null or its int values
// we have a List<List<int?>>
.Where(x => x.Any() && x.All(y => y.HasValue)) // only select lists which contains only integers
.ToList();
I have a array which looks like this :-
a[53]={ARPNUM-T,
OR1PATTYP-T,
IVNUM-T,
IVDESC-T,
ORDEPT-T,
ARPNAME-T,
ARGNAME-T,
ARPATADDR1-T,
ARPATCITY-T,
ARPATSTATE-T,
ARPATZIP-N,
ARSEX-T,
ARBIRTH-N,
ARSSN-T,
ARMARRY-T,
ARADMDT-N,
ARDISDT-N,
ARPEMP-T,
ARPHY1-T,
ARPHYNM1-T,
ARMRNUM-T,
ARGUARSSN-T,
ARPHONE-T,
AREMPLYR-T,
ARADDR1-T,
ARSTATE-T,
ARZIP-N,
ARPATPHONE-N,
ARDIAG01-T,
ISSUBNAME-T,
ISCOMPCD-T,
ISCONAME-T,
ISCONTRAC-T,
ISGROUP-T,
ISPRIMARY-T,
ISCOADDR-N,
ISCOCITST-T,
ISPATREL-T,
ISCERTNO-T,
ISCOZIP-N,
ISSUBNAME-T,
ISCOMPCD-T,
ISCONAME-T,
ISCONTRAC-T,
ISGROUP-T,
ISPRIMARY-T,
ISCOADDR-N,
ISCOCITST-T,
ISPATREL-T,
ISCERTNO-T,
ISCOZIP-N,
ARCITY-T}
There are some repeated values like ISSUBNAME-T,ISCOMPCD-T.
i need to fill the array a to array b
where repeated value will be suffixed by the number of times of repetition ,
For eg - if ISSUBNAME-T is repeated 3 times then ISSUBNAME-T_3 .
I have tried a code:-
for (int d = 1; d < 53; d++)
{
b[0] = a[0];
for (int k = 1; k < d; k++)
{
int count = 0;
//b[d] = a[d];
if (a[d] == a[d - k])
{
count++;
if (count > 0)
{
b[d] = a[d] + "_" + count + "";
}
else
{
b[d] = a[d];
}
//Console.WriteLine(count);
}
//Console.WriteLine(count);
}
//Console.WriteLine(count);
}
But it's not showing correct output.
Group array items by their values. Then check if group contains more than one item. If so, then return formatted item value, otherwise simply return item value:
string[] b = a.GroupBy(i => i)
.Select(g => g.Count() > 1 ?
String.Format("{0}_{1}", g.Key, g.Count()) : g.Key)
.ToArray();
Query syntax (easily allows to calculate group length only once):
var query = from i in a
group i by i into g
let count = g.Count()
select count > 1 ? String.Format("{0}_{1}", g.Key,count) : g.Key;
string[] b = query.ToArray();
UPDATE: If you want to keep all items and have incremental suffixes
string[] b = a.GroupBy(e => e)
.SelectMany(g => g.Count() == 1 ?
g.Take(1) :
g.Select((e,i) => String.Format("{0}_{1}", e,i+1))
.ToArray();
UPDATE 2: If you want also preserving original order, then simple loop and dictionary will be simpler
string[] b = new string[a.Length];
var duplicatedItems = a.GroupBy(a => a)
.Where(g => g.Count() > 0)
.ToDictionary(g => g.Key, g => g.Count());
for(int i = b.Length - 1; i >= 0 ; i--)
{
string item = a[i];
if (!duplicatedItems.ContainsKey(item))
{
b[i] = item;
continue;
}
b[i] = String.Format("{0}_{1}", item, duplicatedItems[item]);
duplicatedItems[item]--;
}
Linq query for comparison
string[] b =
a.Select((e,i) => new { Item = e, Index = i })
.GroupBy(x => x.Item)
.SelectMany(g => g.Count() == 1 ?
g.Take(1) :
g.Select((x,i) => new {
Item = String.Format("{0}_{1}", x.Item, i+1),
Index = x.Index
}))
.OrderBy(x => x.Index)
.Select(x => x.Item)
.ToArray();
I have an array of 2000 strings. The strings are: "art", "economy", "sport" and "politic". I want to group each 500 elements and get their counts
Could anyone help please?
Another solution:
var count = 0;
var dictionaries =
strings.GroupBy(s => count++ / 500)
.Select(g => g.Distinct().ToDictionary(k => k, k => g.Count(s => s == k)))
.ToList();
This will create a List<Dictionary<string, int>>. Each dictionary represents a tally of 500 elements (or possibly less for the last dictionary), where the keys are strings and the values are the number of occurrences of the string among the 500 elements the dictionary represents.
There is no requirement to hardcode all the possible values that may be encountered.
For the maximum possible performance you can also use this version:
var count = 0;
var dictionaries =
strings.GroupBy(s => count++ / 500)
.Select(g => g.Aggregate(
new Dictionary<string, int>(),
(d, w) => { d[w] = (d.ContainsKey(w) ? d[w] + 1 : 1); return d; })
)
.ToList();
This version iterates over each element in your source array exactly once. The output is in the same format as the first version.
var result = strings.Select((s, i) => new { s, i })
.GroupBy(x => x.i / 500)
.Select(x => x.GroupBy(y => y.s)
.Select(z => new {
Name=z.Key,
Count=z.Count()
}).ToList())
.ToList();
Try
var grouping = Enumerable.Range(0,2000)
.Select(i => i / 500)
.Zip(Strings, (i,s) => new { Group = i, Str = s})
.GroupBy(anon => anon.Group,
anon => anon.Str,
(key,g) => new
{
Key = key,
Art = g.Count(str => str == "art"),
Economy = g.Count(str => str == "economy"),
Politic = g.Count(str => str == "politic"),
Sport= g.Count(str => str == "sport")
});
foreach(anon in grouping)
{
//textbox logic OP will have to change to suit
TextBox1.WriteLine(String.Format("Group: {0}", anon.Key));
TextBox1.WriteLine(String.Format("Art: {0}",anon.Art));
TextBox1.WriteLine(String.Format("Economy: {0}",anon.Economy ));
TextBox1.WriteLine(String.Format("Politic: {0}",anon.Politic ));
TextBox1.WriteLine(String.Format("Sport: {0}",anon.Sport));
}
Alternatively (as per Snowbear)
var grouping = Strings.Select((s,i) => new { Group = i / 500, Str = s})
.GroupBy(anon => anon.Group,
anon => anon.Str,
(key,g) => new
{
Key = key,
Art = g.Count(str => str == "art"),
Economy = g.Count(str => str == "economy"),
Politic = g.Count(str => str == "politic"),
Sport= g.Count(str => str == "sport")
});
foreach(anon in grouping)
{
//textbox logic OP will have to change to suit
TextBox1.WriteLine(String.Format("Group: {0}",anon.Key + 1));
TextBox1.WriteLine(String.Format("Art: {0}",anon.Art));
TextBox1.WriteLine(String.Format("Economy: {0}",anon.Economy ));
TextBox1.WriteLine(String.Format("Politic: {0}",anon.Politic ));
TextBox1.WriteLine(String.Format("Sport: {0}",anon.Sport));
}
int CountElementsInGroup = 500;
//from 500 to 1000
int NumberGroup = 2;
string[] GroupTypes = new string[4] { "art", "economy", "sport", "politic" };
//Fill example array
string[] arr = new string[2000];
Random rand = new Random();
for (int i = 0; i < arr.Length;i++ )
arr[i] = GroupTypes[rand.Next(0, 3)];
var res = (from p in arr.Skip((NumberGroup - 1) * CountElementsInGroup).Take(CountElementsInGroup)
group p by p into g
select new GroupCountClass { GroupName = g.Key, GroupCount = g.Count() });
textBox1.Text = "";
foreach (GroupCountClass c in res)
{
textBox1.Text += String.Format("GroupName:{0} Count:{1};",c.GroupName,c.GroupCount);
}