A good idea is to set all of the "" (blank cells) to NA before any further analysis.
If you are reading your input from a file, it is a good choice to cast all "" to NAs:
foo <- read.table(file="Your_file.txt", na.strings=c("", "NA"), sep="\t") # if your file is tab delimited
If you have already your table loaded, you can act as follows:
foo[foo==""] <- NA
Then to keep only rows with no NA you may just use na.omit()
:
foo <- na.omit(foo)
Or to keep columns with no NA:
foo <- foo[, colSums(is.na(foo)) == 0]