Before you run DESeq2, you need to understand what those numbers in your count matrix actually represent. This post explains what RNA-seq count data is, why raw counts are misleading, and exactly what format DESeq2 expects.
Bulk RNA-seq tells you the average gene expression of millions of cells at once. Single-cell RNA-seq tells you what every individual cell is doing. Here is how the technology works, how the data is analyzed, and how to know if you need it.
If R is a smart phone, Bioconductor is the App Store for biology. This post explains why bioinformatics has its own package repository, why it’s better than CRAN for scientists, and how to keep your biological analysis reproducible.