How to select columns from a Dataset using Seq<String> in Java?

Question

I have a Seq and need to use it to select columns in Java

I know about the function .select(String col, Seq<String> cols) but I don't have the first column name.

df.columns returns an array with the names of the columns. — philantrovert
– philantrovert, Commented Jul 29, 2019 at 9:51
@philantrovert that does it, but why wouldn't they just keep a .select(Seq<String> cols) method — maigar
– maigar, Commented Jul 29, 2019 at 10:02

vinsce · Accepted Answer · 2019-07-29 11:01:07Z

1

If you want to select using a Seq<String> you can split the Seq extracting the first element separately:

Seq<String> columns = /* ... */;

Dataframe<Row> newDf = df.select(
    columns.apply(0), // first element
    columns.slice(1, columns.size()) // from the second to the end
);

maybe check the length of columns first, to avoid IndexOutOfBoundsException

edited Jul 29, 2019 at 11:01

answered Jul 29, 2019 at 10:55

vinsce

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1 Comment

maigar Over a year ago

select function takes in input (String,Seq<String>) but slice returns Scala iterable, so had to do toSeq() to it. columns.slice(...).toSeq()

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