When you want to omit rows in your dataframe that have NA's in particular colums.

na.omit.somecols.r

na.omit.somecols <- function(data, noNAsInTheseCols, allOutputCols = names(data)) {
    # usage: na.omit.somecols(my_dataframe, c("col1", "col2")).  You can also supply a vector of names (allOutputCols) if you just want certain columns returned.
    completeVec <- complete.cases(data[, noNAsInTheseCols])
    return(data[completeVec, allOutputCols])
}