logical subsetting

[chloevdb]

add
in logical subsetting vector tricks add this:
!is.na(snp_genes)
snp_genes[!is.na(snp_genes)]

[chloevdb]

add exercise to vector tricks (do the below and compare the difference in output)

c("ACTN3", "AR") %in% snp_genes
snp_genes %in% c("ACTN3", "AR")