[BioC] edgeR topTags output (logFC)

Susan [guest] guest at bioconductor.org
Tue Aug 27 03:28:03 CEST 2013

I'm just wanting to confirm my understanding of the edgeR topTags() output.  I'm using a design matrix with many coefficients (76 genotypes, 2 treatments[sun, shade]).  

1) In the topTags output, I am looking at logFC which represents the estimated or predicted means -- NOT coefficients, correct?  

2) I have selected one parental genotype to be my reference genotype, and I am comfortable interpreting the logFC values for the other genotypes as comparisons to this genotype.  I have selected one treatment as the reference (sun).  When I see the logFC values for 'trtshade', I assume this is also in comparison to the reference genotype in the reference treatment.  

My question is about looking at 'geno2.trtshade' values - are these values in comparison to 'trtshade' or 'geno2' or the reference genotype/reference treatment values?  

For example:  this is calling glmLRT with coef = grep("trt", colnames(Design)) to identify treatment effects

           Row.names       logFC.trtsha    logFC.genoIL1.1.trtsha   logCPM        LR        PValue           FDR
1 Solyc08g078300.2.1    0.9440264           -0.379030370 4.207443 1135.8061 1.450273e-188 1.637938e-184
2 Solyc06g060830.2.1    0.9630343            0.038988710 4.511893 1095.1525 2.539194e-180 1.433883e-176
3 Solyc06g067910.2.1    1.2468599           -0.096499016 4.795789 1040.5813 2.722511e-169 1.024935e-165
4 Solyc06g008580.2.1    1.1500683           -0.451731914 3.300982  696.1677 6.043868e-101  1.706486e-97
5 Solyc07g017600.2.1    0.5026292            0.007208458 5.209938  694.2070 1.451776e-100  3.279271e-97
6 Solyc10g083760.1.1   -0.2877568            0.045952894 7.033394  651.8629  2.232759e-92  4.202796e-89

Thanks so much!

 -- output of sessionInfo(): 

> sessionInfo()
R version 3.0.1 (2013-05-16)
Platform: x86_64-pc-linux-gnu (64-bit)

 [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C         LC_TIME=C            LC_COLLATE=C         LC_MONETARY=C        LC_MESSAGES=C        LC_PAPER=C          

attached base packages:
[1] splines   stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] ggplot2_0.9.3.1 reshape_0.8.4   plyr_1.8        edgeR_3.2.3     limma_3.16.4   

loaded via a namespace (and not attached):
 [1] MASS_7.3-26        RColorBrewer_1.0-5 colorspace_1.2-2   dichromat_2.0-0    digest_0.6.3       grid_3.0.1         gtable_0.1.2       labeling_0.1      
 [9] munsell_0.4        proto_0.3-10       reshape2_1.2.2     scales_0.2.3       stringr_0.6.2      tools_3.0.1       

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