How to use Select with multiple lists?

Question

How to use Select with multiple lists?

FranK Duc 121

Hello,

I tried to iterate from 2 different lists.

var listm = new List<double>();
 listm.Add(Close.GetValueAt(CurrentBar));

 var listf = new List<double>();
 listf.Add(nearclose);


  var resulto =
     from li in listm
     from lis in listf
     select li;

 foreach (var resul in resulto)
 {


 fibo2 = (resul - lowPrice0) / (Ncma - lowPrice0);

 Print("num"+resul);
 }

The Select part bugs me.

How can i select both li and lis. With strings i could do select $"{ li } { lis}";

What about a double?

Thank you

3 answers

Your answer

Answer 1

Viorel 121.3K

If you write:

var resulto =
   from li in listm
   from lis in listf
   select new { li, lis };

foreach( var resul in resulto )
{
   Console.WriteLine( $"{resul.li} {resul.lis}" );
}

then you will obtain all of the combinations.

Maybe you need this:

var resulto2 = listm.Zip( listf, ( li, lis ) => new { li, lis } );

foreach( var resul in resulto2 )
{
   Console.WriteLine( $"{resul.li} {resul.lis}" );
}

FranK Duc 121

Hello Viorel,

I get an error: NinjaScript File Error Code Line Column
NEWSDBA.cs Operator '-' cannot be applied to operands of type 'AnonymousType # 1' and 'double' CS0019 157 17

with both solutions.

I tried this:

 var listm = new List<double>();
listm.Add(Close.GetValueAt(CurrentBar));

 var listf = new List<double>();
 listf.Add(nearclose);


          var resulto2 = listm.Zip( listf, ( li, lis ) => new { li, lis } );

                 foreach( var resul in resulto2 )
                 {
                   fibo2 = (resul - lowPrice0) / (Ncma - lowPrice0);

                      Print("num"+resul);
                 }

Viorel 121.3K Reputation points

2021-06-08T15:50:51.92+00:00

If you want to use li (from listm), then write something like this:

fibo2 = (resul.li - lowProce0) / (Ncma - lowPrice0);

I.e. use resul.li or resul.lis instead of resul.
FranK Duc 121 Reputation points

2021-06-08T16:01:04.44+00:00

Is there a way we can pass both of them in the equation? I am not able to create two fibo2 equation. I am trying to create two parallel channel.
Viorel 121.3K Reputation points

2021-06-08T18:05:40.797+00:00

I think that it is possible if you re-explain what do you mean.
FranK Duc 121 Reputation points

2021-06-08T18:11:37.477+00:00

Its like i replied to Karen.

I cant repeat fibo2 = (resul.li and resul.lis- lowPrice0) / (Ncma - lowPrice0); 2 times

I need both element to be passed in the same equation to avoid:

fibo2 = (resul.li- lowPrice0) / (Ncma - lowPrice0);
and
fibo2 = (resul.lis - lowPrice0) / (Ncma - lowPrice0);

Would of been nice if this was working:

foreach( var resul in resulto2 )
{
fibo2 = (resul - lowPrice0) / (Ncma - lowPrice0);
}

This way both element of the lists would of been process seperately.

ty
Viorel 121.3K Reputation points

2021-06-08T18:26:04.853+00:00

Currently fibo2 is double. What new data type to use for fibo2 to implement two parallel channels?
FranK Duc 121 Reputation points

2021-06-08T18:41:20.96+00:00

Yes fibo2 is double.

I am not sure i follow you. Let me explain you something maybe it will be more obvious.

I have 2 lists: listm and listf. The first one contain the close price and the second one will contain the price closest to the close price, i call it nearclose.

If the first list, listm is been process into:

foreach( var item in listm )
{
fibo2 = (item - lowPrice0) / (Ncma - lowPrice0); //item is close price.
}

Than fibo2 pass throught a series of formulas and in the end return a value for nearclose. (i didnt add that part of the code, too big)
nearclose CANT produce a value until close price has been process first in fibo2 equation.

My idea is if i iterate both lists at the same time nearclose will have a value i can reuse.

Once nearclose get a value i want to use a for loop to reintroduce nearclose in fibo2 and get the next value of nearclose. Its like a snake eating its own tail.
Viorel 121.3K Reputation points

2021-06-08T18:57:04.303+00:00
Maybe you need something like this:

double v = Close.GetValueAt(CurrentBar); double nearclose; do { double fibo2 = (v - lowPrice0) / (Ncma - lowPrice0); nearclose = … big part not shown … v = nearclose; } while ( … );

It calculates nearclose, then use it to calculate the next fibo2 in a loop. You should decide what condition to put in ‘while ( … )’ to terminate the loop. (Maybe when nearclose is equal or almost equal to previous v).
FranK Duc 121 Reputation points

2021-06-08T19:07:16.347+00:00

In fact the logic is that close price enter first in fibo2 equation:

fibo2 = (Close.GetValueAt(CurrentBar) - lowPrice0) / (Ncma - lowPrice0);

fibo2 is process in the big part not shown.

at the end of the big part nearclose which is a private double return a value.

the idea is to return that value (nearclose) in:

fibo2 = (nearclose - lowPrice0) / (Ncma - lowPrice0);

at the end of the big part nearclose return a new value that we send back again

fibo2 = (nearclose - lowPrice0) / (Ncma - lowPrice0); ... and so on.

The problem nearclose wont produce a value until Close.GetValueAt(CurrentBar) has been process first: fibo2 = (Close.GetValueAt(CurrentBar) - lowPrice0) / (Ncma - lowPrice0);

Thats why i thought by using two lists i could process both Close.GetValueAt(CurrentBar) and nearclose at the same time and then recycle nearclose again and again with for loop or while loop.

I am out of idea.

TY
Timon Yang-MSFT 9,606 Reputation points

2021-06-10T08:22:47.867+00:00

@FranK Duc
Can we jump out of this actual problem and re-use a short piece of code to simulate a comparable situation?
I watched the information you provided repeatedly, but unfortunately, I still can't understand the logic of the need until now. I would love to help, but I don’t know where to start.
FranK Duc 121 Reputation points

2021-06-10T11:26:26.1+00:00

I did here: https://learn.microsoft.com/en-us/answers/questions/429084/how-to-use-count-if-you-return-a-variable-in-a-lis.html?childToView=429661#answer-429661

Answer 2

Karen Payne MVP 35,561

Here is a lambda example

private static void Example()  
{  
    var list1 = new List<double>() {1.1, 1.2, 1.3};  
    var list2 = new List<double>() {2.1, 2.2, 2.3};  
  
    var result = list1.Zip(list2, (n, w) => new  
    {  
        Value1 = n,   
        Value2 = w  
    });  
      
    foreach (var item in result)  
    {  
        Console.WriteLine($"{item.Value1} - {item.Value2}");  
    }  
  
}

Another method

using var enumerator1 = list1.GetEnumerator();  
using var enumerator2 = list2.GetEnumerator();  
  
while (enumerator1.MoveNext() && enumerator2.MoveNext())  
{  
    var item1 = enumerator1.Current;  
    var item2 = enumerator2.Current;  
    Console.WriteLine($"{item1} - {item2}");  
}

FranK Duc 121 Reputation points

2021-06-08T15:32:51.913+00:00

Hello Karen,

I also tried your solution. But how can i get to pass both Value1 = n,
Value2 = w in my equation.

I cant repeat fibo2 = (Value1 and Value2- lowPrice0) / (Ncma - lowPrice0); 2 times

I need both Values to be passed in the same equation to avoid:

fibo2 = (Value1- lowPrice0) / (Ncma - lowPrice0);
and
fibo2 = (Value2- lowPrice0) / (Ncma - lowPrice0);

TY

Answer 3

Karen Payne MVP 35,561

In regards to

I need both Values to be passed in the same equation to avoid:

You need a container that holds both values or two variables as otherwise you can't do what you are after. Also, this is not part of the original question which is to iterate two list, nothing about calculations which I just answered.

Webmasters Pride 1 Reputation point

2021-06-10T11:37:32.297+00:00

Thanks, I forgot about the container

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How to use Select with multiple lists?

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