DESeq2: Contrast for two conditions combined versus one condition (A+B_vs_C)
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bioinf ▴ 10
@bioinf-12080
Last seen 6 months ago
United States

Hi,

Below is my samples and conditions info:

Sample_ID        Conditions
1                        A
2                        A
3                        A
4                        B
5                        B
6                        B
7                        C
8                        C
9                        C

For A_vs_C, I followed:

res_A_vs_C= lfcShrink(dds, contrast=c("Conditions", "A", "C"), type='ashr')

Now, I want to compare samples with A and B conditions together versus condition C (A+B_vs_C). How can I do that from the above dds (if there is a way)?

Or do I need to group A+C and create a new column, and then run a new DESeq()? Please guide.

Thanks.

DESeq2 contrasts • 576 views
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ATpoint ★ 4.5k
@atpoint-13662
Last seen 3 hours ago
Germany

See previous threads Using the "listValues" argument of DESEQ in multiple group comparisons

listValues is the keyword.

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Thank you ATpoint ! Considering I used C after A in my last comparison, so this one would be:

res_AB_vs_C = lfcShrink(dds, contrast = list(c("A", "B"), "C"),  listValues=c(-1/2, 1)), type='ashr')

or should I use: (will the order matter? and If so, then I will need to do res_C_vs_A instead of res_A_vs_C)

res_C_vs_AB = lfcShrink(dds, contrast = list("C", c("A", "B"),  listValues=c(1, -1/2)), type='ashr')

Thanks.

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It should not matter, only the sign of the logFC will be other. I always adjust this to the story I want to tell. Say you do treatment vs normal then in my head treatment effects should have a positive logFC in plots etc, so I would put treatment vs (control1,control2)/2.

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