# MaAsLin2: Comparing one value to multiple values simultaneously

**URL:** <https://forum.biobakery.org/t/maaslin2-comparing-one-value-to-multiple-values-simultaneously/9000>\
**Category:** MaAsLin\
**Created:** [July 14, 2026, 8:34pm UTC](https://forum.biobakery.org/t/maaslin2-comparing-one-value-to-multiple-values-simultaneously/9000 "2026-07-14T20:34:59Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Antara13](https://avatars.discourse-cdn.com/v4/letter/a/9f8e36/32.png) [@Antara13](https://forum.biobakery.org/u/Antara13)\
**Post date:** [July 14, 2026, 8:34pm UTC](https://forum.biobakery.org/t/maaslin2-comparing-one-value-to-multiple-values-simultaneously/9000/1 "2026-07-14T20:34:59Z")

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I’m currently using MaASLin2, and I’m using it to find associations between 4 parulid warblers and the insect prey in their diet. I’ve been thinking of creating a visual for it with a heatmap a bit like this-

 ![Screenshot 2026-07-14 163456](https://canada1.discourse-cdn.com/flex027/uploads/biobakery/original/2X/6/6276033dac9d899fe19da9e5e6ad4d1c0f53bd5c.jpeg)

The snag I’ve been experiencing is that the coefficient value for each species with reference to the other species is a little different. So if I need to put in a effect size value for say Bird 1 for the insect 1 Leucauge venusta, its coeff in reference to Bird 2 is 4.8, but its coeff in reference to Bird 3 is 3.6. Is there any way I can get a single value for Bird 1 in reference to both Bird 2 and 3?

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**Author:** ![WillNickols](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.biobakery.org/willnickols/32/3223_2.png) [@WillNickols](https://forum.biobakery.org/u/WillNickols)\
**Post date:** [July 14, 2026, 8:57pm UTC](https://forum.biobakery.org/t/maaslin2-comparing-one-value-to-multiple-values-simultaneously/9000/2 "2026-07-14T20:57:00Z")

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Hi,

We have some information on interaction effects [in the MaAsLin 3 tutorial](https://github.com/biobakery/biobakery/wiki/MaAsLin3#43-interactions) which might be helpful.

I’m not sure that I quite follow for your case; are you saying you have 9 groups, one for each cell in that 3x3? You’ll always need a comparison to at least one reference group since the coefficients and significance values from a linear regression tell you the difference between a particular group and the reference. Is it possible to select one of those groups as the reference in MaAsLin 2/3 and then report all coefficients relative to that reference group?

Will

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**Author:** ![Antara13](https://avatars.discourse-cdn.com/v4/letter/a/9f8e36/32.png) [@Antara13](https://forum.biobakery.org/u/Antara13)\
**Post date:** [July 15, 2026, 6:57pm UTC](https://forum.biobakery.org/t/maaslin2-comparing-one-value-to-multiple-values-simultaneously/9000/3 "2026-07-15T18:57:42Z")

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I see. That might not work out for my planned visualization, but I can definitely use the presence of a reference group for other analyses, thanks!