Tool in Mylly: Relation algebra / Keep | fi

Keep selected attributes

The ”keep” operation projects an input relation to the selected attributes.

The input and output relations are represented as TSV files.


  • zero or more attributes

Attributes are presented as menus that list the attributes that the relation has. EMPTY indicates that the parameter is not used.

Selecting the same attribute more than once is harmless.

(Selecting no attributes, by leaving every attribute parameter at EMPTY, produces a relation with no attributes. There are two such relations.)


The input relation consists of word forms annotated with sentence and token numbers and lemmas.

word tok sen lemma
on 1 3 olla
se 2 3 se
niin 3 3 niin
on 1 5 olla
ei 1 4 ei
ole 2 4 olla

When the word form and lemma are kept, the two occurrences of olla as on melt into one record.

lemma word
ei ei
se se
niin niin
olla on
olla ole

When only the lemma is kept, all three occurrences of olla melt into one record.


Related tools

  • drop
  • keep with count
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