DESeq2 different log2FC and p-value filtering parameters results comparison
1
0
Entering edit mode
User000 • 0
@ea03770f
Last seen 2.1 years ago
Italy

Hello,

I have created two datasets with two different filtering parameters as following:

log2folgchange = 0:

contrast = (list(c("treated_1","treated_2"),("control"),listValues = c(1/2,-1)))
resLFC <- lfcShrink(dds, contrast=contrast, res=res, type="ashr")
up <- res[which(resLFC$log2FoldChange > 0 & resLFC$padj < 0.01),]
down <- res[which(resLFC$log2FoldChange < 0 & resLFC$padj < 0.01),]

log2foldchange = 1:

up <- res[which(resLFC$log2FoldChange > 1 & resLFC$padj < 0.01),]
down <- res[which(resLFC$log2FoldChange < -1 & resLFC$padj < 0.01),]

In the dataset at log2FC=0 I see some genes that are not in the dataset of log2FC=1 even thought the log2FC is equal to -1.29 and padj is 0.005, si it should be in my dataset with log2F= 1 I presume. Why does that happen?

gene    baseMean    log2FoldChange  lfcSE   stat    pvalue  padj
ENSG000000XXXX  74,9062387275475    -1,29048864731255   0,377167404326021   -3,4215275034665    0,000622704264736   0,00590226764893
log2 DESeq2 • 3.2k views
ADD COMMENT
0
Entering edit mode
Basti ▴ 780
@7d45153c
Last seen 23 hours ago
France

I think you made something wrong, try setdiff(up2$gene,up$gene)with up <- res[which(resLFC$log2FoldChange > 0 & resLFC$padj < 0.01),] and up2 <- res[which(resLFC$log2FoldChange > 1 & resLFC$padj < 0.01),]

ADD COMMENT
0
Entering edit mode

I checked also with excel before and now with your code, In down log2FC=0 I have 1371 genes and in log2FC=1 616, with your code I get 616, but I do not see the gene in the list anyway....

ADD REPLY
0
Entering edit mode

Check your objects are correct and re-run your code entirely, there might be an overlap between different objects because you can't have more genes applying the threshold of log2FC< -1 than log2FC<0, this is strictly impossible. If you try with an random dataset, you can see that what you are observing can't happen :

set.seed(1)
dds <- makeExampleDESeqDataSet(n=500,betaSD=1)
dds <- DESeq(dds)
res <- results(dds)

resultsNames(dds)
resLFC <- lfcShrink(dds=dds, coef=2, type="ashr")

up <- res[which(resLFC$log2FoldChange > 1 & resLFC$padj < 0.01),]
down <- res[which(resLFC$log2FoldChange < -1 & resLFC$padj < 0.01),]

up2 <- res[which(resLFC$log2FoldChange > 1 & resLFC$padj < 0.01),]
down2 <- res[which(resLFC$log2FoldChange < -1 & resLFC$padj < 0.01),]

setdiff(up2$gene,up$gene)
ADD REPLY
0
Entering edit mode

Thanks for your answer, infact I do not have more genes in log2FC=-1 dataset, as I wrote above for log2FC=0 I have 1371 genes and log2FC=-1 I have 616 genes. All log2FC values higher than -1 that are not the in log2FC=-1 dataset (around 125 genes) do not exceed log2FC value more than 1.5/-1.5 for up and down, respectively. I think there is some explanation in the DESeq2 algorithm.

ADD REPLY
0
Entering edit mode

There is nothing related to DESeq2 in your code, this is a simple filter on a DESeq2 result. Have you ran my example code ?Certainly there is something wrong in your code because what you observe is mathematically impossible (if you add a small example of your dataset in your post I would be glad to help).

ADD REPLY
0
Entering edit mode

I get 755 genes, exaclty the difference between 1371 and 616. But the problem is that some genes according to my filtering should be in the log2fc=1 dataset and they are missing. So I do not understand how this can solve the problem...

ADD REPLY
0
Entering edit mode

If you share example dataset we could have a look, otherwise there us something wrong with your code that we can't solve with information available for us

ADD REPLY
0
Entering edit mode

I solved the problem. It should have been resLFC also outside of bracket like this:

up <- **resLFC**[which(resLFC$log2FoldChange > 0 & resLFC$padj < 0.01),]
down <- **resLFC**[which(resLFC$log2FoldChange < 0 & resLFC$padj < 0.01),]
ADD REPLY

Login before adding your answer.

Traffic: 866 users visited in the last hour
Help About
FAQ
Access RSS
API
Stats

Use of this site constitutes acceptance of our User Agreement and Privacy Policy.

Powered by the version 2.3.6