Spark Dataframe select based on column index

Question

How do I select all the columns of a dataframe that has certain indexes in Scala?

For example if a dataframe has 100 columns and i want to extract only columns (10,12,13

Answer 1

@user6910411's answer above works like a charm and the number of tasks/logical plan is similar to my approach below. BUT my approach is a bit faster.
So,
I would suggest you to go with the column names rather than column numbers. Column names are much safer and much ligher than using numbers. You can use the following solution :

val colNames = Seq("col1", "col2" ...... "col99", "col100")

val selectColNames = Seq("col1", "col3", .... selected column names ... )

val selectCols = selectColNames.map(name => df.col(name))

df = df.select(selectCols:_*)

If you are hesitant to write all the 100 column names then there is a shortcut method too

val colNames = df.schema.fieldNames