Odp: calculations with vectors of unequal length
Hi r-help-bounces at r-project.org napsal dne 27.04.2011 13:30:13:
Hi there, this is probably simple but I can't seem to figure it out by myself... I have two dataframes (df.1 and df.2): df.1 <- data.frame(year=factor(rep(1:3,3)), level=rep(letters[1:3],3), number=c(11:19)) df.2 <- data.frame(year=factor(c(1:5)), number=c(21:25)) I would like to create a new variable df.1$new, which is supposed to be the sum of each element of df.1$number and those elements of df.2$number, where df.2$year equals df.1$year.
merge(df.1,df.2, by.x="year", by.y="year", all.x=T) year level number.x number.y 1 1 a 11 21 2 1 a 17 21 3 1 a 14 21 than you can sum last 2 columns. I believe that sqldf package can do what you want more efficiently but I do not use it so I do not know exact syntax. Regards Petr
What would be the most efficient way of doing this? Regards, EH
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