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f#deedle

Select a subset of columns (ie. filter data frame by collection of column keys)

There are some examples of how to get a single column from a data frame like this.

people?Age
people.["Age"]
people.GetColumn("Countries")

but how can you get a subset of multiple columns? For example, I would like to be able to do something like: 

people.[["age";"Countries"]]

or

people.GetColumn(["age";"Countries"])

and have it return a data frame with just those two columns/series. Is there a simple way to do this?

Solution

  • Using Frame.sliceCols is one way to do this, but you can use the slicing syntax too. The trick is to use slicing on people.Columns rather than directly on the frame:

    people.Columns.[["age";"Countries"]]

    The motivation for this is that you might want to slice the rows as well, in which case you can do people.Rows.[ [1;3;5 ]. If your frame has ordered row index, you can select a range and do people.Rows.[1 .. 10].