# Order of operations? Prev then normalisation or normalisation then prev?

**URL:** <https://forum.biobakery.org/t/order-of-operations-prev-then-normalisation-or-normalisation-then-prev/4524>\
**Category:** MaAsLin\
**Created:** [December 14, 2022, 11:39am UTC](https://forum.biobakery.org/t/order-of-operations-prev-then-normalisation-or-normalisation-then-prev/4524 "2022-12-14T11:39:30Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![aylafr](https://avatars.discourse-cdn.com/v4/letter/a/ecc23a/32.png) [@aylafr](https://forum.biobakery.org/u/aylafr)\
**Post date:** [December 14, 2022, 11:39am UTC](https://forum.biobakery.org/t/order-of-operations-prev-then-normalisation-or-normalisation-then-prev/4524/1 "2022-12-14T11:39:30Z")

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hello,

I was wondering how the order of operations is in maaslin.

If I do a min\_prevalence = 0.1 and normalization = “CLR” is one done before the other as default or will it change depending on the order inputted in my code?

Thank you

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**Author:** ![andrewGhazi](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.biobakery.org/andrewghazi/32/2950_2.png) [@andrewGhazi](https://forum.biobakery.org/u/andrewGhazi)\
**Post date:** [December 14, 2022, 9:33pm UTC](https://forum.biobakery.org/t/order-of-operations-prev-then-normalisation-or-normalisation-then-prev/4524/2 "2022-12-14T21:33:48Z")

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As you can see in the source, the prevalence is used first (lines 843 then 853-6) before the normalization (lines 884-5).

> <https://github.com/biobakery/Maaslin2/blob/master/R/Maaslin2.R#L843>