Problems formatting date into format “%Y-%m” [duplicate]

Answer 1

A year and a month do not make a date. You need a day also.

d <- data.frame(V1=c("1950-12","1951-01"))
as.Date(paste(d$V1,1,sep="-"),"%Y-%m-%d")
# [1] "1950-12-01" "1951-01-01"

You could also use the yearmon class in the zoo package.

library(zoo)
as.yearmon(d$V1)
# [1] "Dec 1950" "Jan 1951"