What is the simple past of the verb to subset? The simple past of set is set. But, I see it written as subsetted, as in:

Each row in the matrix specifies the location of one value, where each column corresponds to a dimension in the array being subsetted."

This is from Advanced R, by Hadley Wickham.

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    There is no such verb. – Ricky Jan 2 '16 at 23:45

The word subset comes from the noun set, meaning collection of things. This is completely unrelated to the verb set, both in meaning and etymologically. The noun comes from Latin, while the verb comes from Old English. So why should the verb subset follow the conjugation of the unrelated verb set?

You might just as easily ask why the verb pellet has a past tense of pelleted, when the past tense of let is let. It's because they're completely unrelated.

  • Analogy. Dove is now an accepted past tense of dive and proven a long-standing accepted past participle of prove, both of which came about by analogy - what marks subset as different that it can't be subject a similar innovation? – Anonym Jan 2 '16 at 23:41
  • @Anonym: I suppose it could have, but mathematicians use subsetted as the past tense of subset. – Peter Shor Jan 2 '16 at 23:48
  • This looks like the correct answer. – Harlan Nelson Jan 3 '16 at 0:28

Subset is not a verb according to every major English dictionary.

If you wanted to use the word as a verb in nonstandard usage, we can look at how similar sounding words are formed in the simple past to try to hazard a guess.

The simple past of offset is offset.

The simple past of reset is reset.

The simple past of upset is upset.

The simple past of typeset is typeset.

The simple past of preset is preset.

The simple past of overset is overset.

The simple past of beset is beset.

The simple past of underset is underset.

So I would propose that the simple past of subset is subset.

To me, subsetted sounds unnatural.

  • Yes, but "... where each column corresponds to a dimension in the array being subset." sounds more unnatural. – Jim Jan 2 '16 at 23:37
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    The past tense of let is let, the past tense of sublet is sublet, the past tense of relet is relet, but the past tense of pellet is pelleted and the past tense of leaflet is leafleted. The meaning makes a difference. And subset has nothing to do with the verb set. – Peter Shor Jan 2 '16 at 23:57
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    @PeterShor And I guess all of the examples in Kyle's list are based on the verb set. Is that right? – WS2 Jan 3 '16 at 1:14

A "set being subsetted" is properly called a superset—also not a verb.

But you should, alas, feel free to say "subsetted" if it gets the point across in a programming situation. Without liberties like these we wouldn't have many manuals at all.

In your example, better ways to get the point across could be by saying "source set," "original set" or "input set."

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