Message-ID: <98c62e1105082313017746c4cf@mail.gmail.com>
Date: 2005-08-23T20:01:14Z
From: alejandro munoz
Subject: merge list entries
dear expeRts,
i would like to merge the data frame entries in a list. for example:
> #input
> myl <- list(q1=data.frame(id=c("Alice", "Bob"), grade=c(90, 49)),
q2=data.frame(id=c("Alice", "Chuck"), grade=c(70, 93)),
q3=data.frame(id=c("Bob", "Chuck"), grade=c(84, 40)))
> #output
> (mydf <- magic(myl))
id grade.1 grade.2 grade.3
1 Alice 90 70 NA
2 Bob 49 NA 84
3 Chuck NA 93 40
my three attempts, and their error messages, follow:
> lapply(myl, merge, by="id", all=TRUE)
Error in as.data.frame(y) : argument "y" is missing, with no default
> lapply(myl[[-1]], merge, y=myl[[1]], by="id", all=TRUE)
Error in lapply(myl[[-1]], merge, y = myl[[1]], by = "id", all = TRUE) :
attempt to select more than one element
> do.call("merge", list(myl[[1]], myl[[-1]], by="id", all=TRUE))
Error in do.call("merge", list(myl[[1]], myl[[-1]], by = "id", all = TRUE)) :
attempt to select more than one element
i can do the merge sequentially, e.g.
m12 <- merge(myl[[1]], myl[[2]], ...)
m123 <- merge(m12, myl[[3]], ...)
but (a) in my actual example i have up to q7, and (b) this looks very
clumsy, even if i wrapped it inside a do loop.
i'd appreciate any help.
alejandro