16.2 select()

select() will select (keep or remove) columns from a data frame.

Select only columns GeneSymbol and DE from geneexp:

select(geneexp, GeneSymbol, DE)

Remove column DE:

select(geneexp, -DE)

Again, a good practice is to save that subset into a new object:

geneexp_selected <- select(geneexp, GeneSymbol, DE)

Let’s combine filter and select: extract (from geneexp) gene symbols of down-regulated genes!

Try by yourself before clicking here!

# Step 1: filter down-regulated genes
down_genes <- filter(geneexp, DE=="DOWN")

# Step 2: extract gene symbols as a data frame with select()
select(down_genes, GeneSymbol)

# Step 2: extract gene symbols as a vector with pull()
pull(down_genes, GeneSymbol)