将月，年和日转换为SAS格式的日期

Question

Ciao, I am in need of assistance in converting month column, year column, and date column, into SAS format date. SAS date value is a value that represents the number of days between January 1, 1960, and a specified date. SAS can perform calculations on dates ranging from AD 1582 to AD 19,900. Dates before January 1, 1960, are negative numbers; dates after January 1, 1960, are positive numbers.Example: month=9,year=1992,day = 1, date=11946

Answer 1

You can use difftime

ss <- "1992-9-15"
difftime(as.Date(ss), as.Date("1960-01-01"))
#Time difference of 11946 days

You don't give a day for your sample date, but working backwards gives the 15th of September 1992.

To store as a numeric do

date_for_SAS <- as.numeric(difftime(as.Date(ss), as.Date("1960-01-01")))
date_for_SAS
#[1] 11946

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Update

If you have a data.frame with three columns day , month and year , you can do the following

df <- data.frame(
    day = c(1:10),
    month = rep(9, 10),
    year = rep(1992, 10))

df$date_for_SAS <- as.numeric(difftime(
    as.Date(sprintf("%s-%s-%s", df$year, df$month, df$day)),
    as.Date("1960-01-01")))
#   day month year date_for_SAS
#1    1     9 1992        11932
#2    2     9 1992        11933
#3    3     9 1992        11934
#4    4     9 1992        11935
#5    5     9 1992        11936
#6    6     9 1992        11937
#7    7     9 1992        11938
#8    8     9 1992        11939
#9    9     9 1992        11940
#10  10     9 1992        11941