I was able to figure it out with sqldf, but I want to be able to achieve the same results in pure R.
Data:
df <- read.table(header=T, text = "year1 year2 year3 year4 signup_date
B U C D 4/10/12
C D B U 2/12/12
U C D U 3/14/05
B NA NA NA 3/7/05
NA NA NA NA 8/3/08
A NA NA NA 4/6/07")
My sqldf query:
df <- sqldf("
SELECT *
FROM data
WHERE year1 NOT IN ('B','C','D','U')
AND year2 NOT IN ('B','C','D','U')
AND year3 NOT IN ('B','C','D','U')
AND year4 NOT IN ('B','C','D','U')
ORDER BY signup_date DESC")
Desired result:
year1 year2 year3 year4 signup_date
8/3/08
A 4/6/07