gvkey = id
data = dataframe
data$t <- NA;
data[data$year = 2005, "t"] <- 1
data[data$year = 2006, "t"] <- 2
data[data$year = 2007, "t"] <- 3
data[data$year = 2008, "t"] <- 4
data[data$year = 2009, "t"] <- 5
data[data$year = 2010, "t"] <- 6
I want to create variable "t":
gvkey year t
1004 2005 1
1004 2006 2
1004 2007 3
1004 2008 4
1004 2009 5
1004 2010 6
1013 2005 1
1013 2006 2
1013 2007 3
1013 2008 4
1013 2009 5
1013 2010 6
.....
Somehow my code does not work. Do you have any idea why?
Is there a more efficient way to run this code?
I am new to R and would really appreciate your help.
column of interest