r - How do I use the lubridate package to calculate the number of months between two date vectors where one of the vectors has NA values? -

i've read lubridate package manual , have queried stack overflow variety of permutations of question have come no answer specific problem.

what i'm trying calculate age in months @ time of event difference between date of birth , specific event date.

as such, imported sas dataset using sas7bdat package , converted sas date variables (dob , event) r objects using following code:

df$dob <- as.date(df$dob, origin="1960-01-01") df$dob1 <- ymd(df$dob)

and same thing event variable:

df$event <- as.date(df$event, origin="1960-01-01") df$event1 <- ymd(df$event)

however, there na values dob. so, following code want use calculate age (in months).

df$interval <- new_interval(df$dob1,df$event1) df$age1 <- df$interval %/% months(1)

i'm receiving error:

error in est[start + est * per < end] <- est[start + est * per < end] + : nas not allowed in subscripted assignments

what doing wrong? i've tried if/else function perhaps used incorrectly.

(note: sas programmers out there, i'm trying produce same results following function:

if dob ne . tage=floor(intck('month',dob,event)-(day(event)<day(dob)));

simple example using lubridate package

library(lubridate) date1='20160101' date2='20160501' x=interval(ymd(date1),ymd(date2)) x= x %/% months(1) print(x) # answer : 4

O9