Handling NA values in apply and unique

Question

I have a 114 row by 16 column data frame where the rows are individuals, and the columns are either their names or NA. For example, the first 3 rows looks like this:

Answer 1

You were very, very close in your initial solution. But as Aniko remarked, you have to remove NA values before you can use unique.

An example where we first create a similar data.frame and then use apply() as you did -- but with an additional anonymous function that is used to combine na.omit() and unique():

R> DF <- t(data.frame(foo=sample(c(NA, "Foo"), 5, TRUE), 
                      bar=sample(c(NA, "Bar"), 5, TRUE)))
R> DF
    [,1]  [,2] [,3]  [,4]  [,5] 
foo "Foo" NA   "Foo" "Foo" "Foo"
bar NA    NA   NA    "Bar" "Bar"
R> apply(DF, 1, function(x) unique(na.omit(x)))
  foo   bar 
"Foo" "Bar" 

Answer 2

unique does not appear to have an na.rm argument, but you can remove the missing values yourself before calling it:

A <- matrix(c(NA,"A","A",
             "B", NA, NA,
              NA, NA, "C"), nr=3, byrow=TRUE)
apply(A, 1, function(x)unique(x[!is.na(x)]))

gives

[1] "A" "B" "C"