I have a panel data set like below. But actual data set has several thousands observations. I want to create 14 facotors as a new column "Year_dum" for years 1984-1998 (15 years). I searched for creating dummy variables in r, but could not find a way to do that using year integers. Can anybody please help me to do this in r.
+--------+------+------+------+----------+ | Time | year | Firm | Prod | Year_dum | +--------+------+------+------+----------+ | Jan-84 | 1984 | A | 28.2 | 0 | | Feb-84 | 1984 | A | 26.6 | 0 | | Mar-84 | 1984 | A | 30.3 | 0 | | Apr-85 | 1985 | A | 33.2 | 1 | | May-85 | 1985 | A | 30.1 | 1 | | Jun-85 | 1985 | A | 28.3 | 1 | | Jan-84 | 1984 | B | 28.6 | 0 | | Feb-84 | 1984 | B | 28.9 | 0 | | Mar-84 | 1984 | B | 28.1 | 0 | | Oct-84 | 1984 | C | 28.8 | 0 | | Nov-85 | 1985 | C | 31.6 | 1 | | Dec-86 | 1986 | C | 26.9 | 2 | | Jan-89 | 1989 | C | 28.6 | 5 | | Feb-98 | 1998 | C | 29.6 | 14 | +--------+------+------+------+----------+
This simple data set can be accessed using the following dput.
structure(list(Time = structure(c(6L, 4L, 9L, 2L, 10L, 8L, 6L,
4L, 9L, 12L, 11L, 3L, 7L, 5L, 1L, 1L, 1L), .Label = c("", "Apr-85",
"Dec-86", "Feb-84", "Feb-98", "Jan-84", "Jan-89", "Jun-85", "Mar-84",
"May-85", "Nov-85", "Oct-84"), class = "factor"), year = c(1984L,
1984L, 1984L, 1985L, 1985L, 1985L, 1984L, 1984L, 1984L, 1984L,
1985L, 1986L, 1989L, 1998L, NA, NA, NA), Firm = structure(c(2L,
2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 4L, 1L, 1L, 1L
), .Label = c("", "A", "B", "C"), class = "factor"), Prod = c(28.2,
26.6, 30.3, 33.2, 30.1, 28.3, 28.6, 28.9, 28.1, 28.8, 31.6, 26.9,
28.6, 29.6, NA, NA, NA), Year_dum = c(0L, 0L, 0L, 1L, 1L, 1L,
0L, 0L, 0L, 0L, 1L, 2L, 5L, 14L, NA, NA, NA)), .Names = c("Time",
"year", "Firm", "Prod", "Year_dum"), class = "data.frame", row.names = c(NA,
-17L))
We can try
df$Year_dum <- df$year-min(df$year)
df$Year_dum
#[1] 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1
Or use match
with(df, match(year, unique(year))-1)
#[1] 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1