Question: DESeq2 design and stats question
gravatar for rbronste
22 months ago by
rbronste60 wrote:

So will just list current design first and then get into the question:

rangedCounts <- dba.peakset(Adult_BN_count, bRetrieve=TRUE)

nrows <- 1054182 
ncols <- 12
counts <- matrix(runif(nrows * ncols, 1, 1e4), nrows)

sampleNames<-c("MBV1",    "MBV2",    "MBV3",    "FBV1",    "FBV2",    "FBV3", "MBE7", "MBE8", "MBE9", "FBE1", "FBE2", "FBE3")
sampleSex<-c("male", "male", "male", "female", "female", "female", "male", "male", "male", "female", "female", "female")
sampleTreatment<-c("vehicle", "vehicle", "vehicle", "vehicle", "vehicle", "vehicle", "BB", "BB", "BB", "BB", "BB", "BB")
colData<-data.frame(sampleName=sampleNames, sex=sampleSex, treatment=sampleTreatment)

# Retrieve counts from dba.count without the site interval ranges

counts <- as.matrix(mcols(rangedCounts))

# Construct a SummarizedExperiment

se<-SummarizedExperiment(assays=list(counts=counts),rowRanges=rowRanges, colData=colData)

# DESeq2 analysis

table(sampleSex, sampleTreatment)

dds<-DESeqDataSet(se, design= ~sex + treatment)

dds$group <- factor(paste0(dds$sex, dds$treatment))

design(dds) <- ~0 + group

dds <- dds[ rowSums(counts(dds)) > 1, ]

dds <- DESeq(dds, betaPrior = FALSE)

So my question is about two types of results I am aiming for, group comparisons and pairwise comparisons, results method listed below:

#pairwise comparison

BN_group_male<-results(dds, format = c("GRanges"), contrast=c("group", "maleBB", "malevehicle"))

#group comparison

resFemVeh_BN<-results(dds, lfcThreshold = 1, altHypothesis = "greater", format = c("GRanges"), contrast=c(-1/3, 1, -1/3, -1/3))

My overall goal here is to see:

1. Example: What are the male vs female diff irrespective of treatment etc.

2. Example: What are differential peaks specific to only the Male BB condition and no other.

I am wondering if this is the proper way to get the results for these particular comparisons given the above design? 

ADD COMMENTlink modified 22 months ago by Michael Love26k • written 22 months ago by rbronste60
Answer: DESeq2 design and stats question
gravatar for Michael Love
22 months ago by
Michael Love26k
United States
Michael Love26k wrote:

The first is straightforward: a comparison of the BB vs vehicle in males. The second is a comparison of the second group against an average of the others. Use plotCounts to get a sense of the top genes that the results tables are pulling out.

ADD COMMENTlink written 22 months ago by Michael Love26k


My central question here is whether the design makes sense for the two ways in which I am retrieving results? 

Also, in addition, I was noticing that when I lfcThreshold the #1 result type (a comparison of the BB vs vehicle in males) at the same cutoff as #2 I get pretty much no diff peaks (hence no lfc thresholding in the above #1 results formula), and wondering why that might be? Thanks again.

ADD REPLYlink modified 22 months ago • written 22 months ago by rbronste60

"Male vs female irrespective of treatment" you could get by averaging male vs female in each group. So putting 1/2 and -1/2 in the contrast. You don't seem to have anything like that in your code.

One vs the rest you can get with your second contrast.

Getting no diff peaks with cutoff: do some exploration and see if you find the answer. I would look at e.g. an MA plot of the results table.

ADD REPLYlink written 22 months ago by Michael Love26k

Ok great thanks will put in that additional comparison, but in terms of the actual contrast I guess it would be the following, for male vs female only:

contrast=c(1/2, -1/3, -1/2, -1/3)

I guess just a little confused in this format for how to specify the comparison, not as much in the vignette. 

Thanks again!

ADD REPLYlink written 22 months ago by rbronste60

Put 1/2 for coefficients associated with M and -1/2 for the coefficients associated with F. This is a bit of a complex contrast because it isn’t represented by any coefficient in the design. There isn’t a M vs F “irrespective” when you are fitting a group for each combination of sex and treatment. You may want to discuss this in more detail with a statistical collaborator. I mostly provide software feedback here, but have limited time for further statistical instruction.

ADD REPLYlink written 22 months ago by Michael Love26k

Thanks again!

ADD REPLYlink written 22 months ago by rbronste60
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