Microsoft.Data.Analysis DataFrame - What is the idiomatic way to fill one column with manipulated values from another?

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chrisxfire asked Apr 27, '22 chrisxfire commented Apr 28, '22

Microsoft.Data.Analysis DataFrame - What is the idiomatic way to fill one column with manipulated values from another?

C# 10 / .NET 6 / Microsoft.Data.Analysis

Given a Microsoft.Data.Analysis DataFrame with two columns, what is the idiomatic way to take values from one column, manipulate them, then use the resulting value to fill the rows of the second column element-wise?

     // Create a DateTime column.
     PrimitiveDataFrameColumn<DateTime> dateTimeCol = new("Dates", 0);
     // Fill it.
     dateTimeCol.Append(DateTime.Now + TimeSpan.FromDays(1));
     dateTimeCol.Append(DateTime.Now + TimeSpan.FromDays(2));
     dateTimeCol.Append(DateTime.Now + TimeSpan.FromDays(3));

     // Create a Ticks column.
     PrimitiveDataFrameColumn<long> ticksCol = new("Ticks", dateTimeCol.Length);

     // Create a DataFrame of the above two columns.
     DataFrame df = new();
     df.Columns.Add(dateTimeCol);
     df.Columns.Add(ticksCol);

At this point, what I want to do is df["Ticks"] = df["Dates"].Ticks. Of course, this doesn't work. I could do this:

     for (int i = 0; i < df.Rows.Count; i++)
     {
         DateTime tempDate = (DateTime) df[i, df.Columns.IndexOf("Dates")];
         df[i, df.Columns.IndexOf("Ticks")] = tempDate.Ticks;
     }

But... is there a better way?

dotnet-csharp dotnet-ml-big-data

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Answer 1 · 2022-04-28T05:45:07.26Z

JackJJun-MSFT answered Apr 28, '22 chrisxfire commented Apr 28, '22

@chrisxfire, Welcome to Microsoft Q&A, based on my research, I find that there is no direct way to give the value like you mentioned.

We could only use loop to do it. Maybe the following code will be more simpler.

 var list = df["Dates"].Cast<DateTime>().Select(i => i.Ticks).ToList();
    
 for (int i = 0; i < list.Count; i++)
 {
     df["Ticks"][i] = list[i];
 }

Hope this could help you.

Best Regards,
Jack

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chrisxfire · Apr 28 at 09:15 PM

Many thanks, Jack.

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