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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?

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1 Answer

JackJJun-MSFT avatar image
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JackJJun-MSFT answered chrisxfire commented

@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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Many thanks, Jack.

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