It is a fairly established terminology in mathematics and programming that one can "index a variable", in the sense of appending a dimension of variability to it (e.g. here and here, respectively). Wiktionary captures index as a verb too.

I am looking for a verb that expresses the contrary action, i.e. to remove an index. Wiktionary includes the verbs "deindex" and "unindex" (as synonymous), albeit with the following definition:

  1. (computing, finance) To remove from an index.

I highlight the "from" preposition, because it shows that definition is not exactly what I'm looking for. I want to remove an index from a variable, and not remove a component of an index (e.g. remove a stock from a stock exchange index).

And yet, the adjective "unindexed" exists, and it is used precisely in the meaning of "not having an index" (e.g. here). Given that "indexed" is the past participle of the verb "to index", we could similarly think of "unindexed" as the past participle of the verb "to unindex", and thus append the meaning of "unindexed" to that verb, thereby validating my desired meaning.

To provide more context, consider a multidimensional variable X, which varies across individuals (indexed as i) and over time (indexed as t). For example, income. In mathematical notation, this is represented as Xit.

I am writing the following phrase:

We cannot eliminate t from Xit unless ...

I would like to use instead:

We cannot unindex t from Xit unless ...

  • 1
    The full OED doesn't recognise unindex, and their entry for de-index only gives the definition To remove indexation to inflation or cost-of-living rates from (pensions or other benefits); to cease to index. But your usage would be perfectly comprehensible to your target audience, so feel free to use it if you want. – FumbleFingers Aug 16 '18 at 15:49
  • The use of v.t. index in the sense of including a variable in an index is not documented, so the question of "undexing" in the sense of pulling the variable out of an index is incorrect. – Kris Aug 17 '18 at 7:18

Index t represents dependence on time. If you remove t from X_it, you are saying something different with your formal expression. Your text should reflect what is happening mathematically, not just restate the change you are making in the symbols.

For example: We cannot remove the time dependence from X_it unless...

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