Hello:
Do you have suggestions for how to aggregate a data.frame using
different functions on different columns?
Consider the following example:
df2aggregate <- data.frame(id=rep(letters[1:4], each=2),
x =c(1:6, NA, NA),
y =c(NA, 1:6, NA),
a =c(NA, NA, LETTERS[1:6]),
stringsAsFactors=FALSE)
# Desired output:
ag1.2 <- data.frame(id=letters[1:4],
x =c(3, 7, 11, NA),
y =c(NA, 2.5, 4.5, NA),
a =c(NA, 'A', 'C', 'E'),
stringsAsFactors=FALSE)
I'm thinking of writing a function Aggregate(x, by, FUN, ...),
where x = data.frame, by = vector of names of columns of x, and FUN =
function that would accept as input a data.frame subset of x and would
return a data.frame FUNout, which would be combined using cbind(x[, by],
FUNout), then rbind over all such subset data.frames. However, before I
write this, I'd like to make sure it doesn't already exist. My current
plan is to add it to the Ecdat package.
Suggestions? Should I study "plyr"? fortune(298) ;-)
Thanks,
Spencer
p.s. library(sos); findFn('aggregate.data.frame') returned 4 matches,
none of which seemed to solve this problem. findFn('aggregate
data.frame') returned 133 matches in 71 package. findFn('aggregate')
returned 734 matches in 282 packages. I failed to find anything useful
in the latter two and with other attempts using RSiteSearch, except for
a reference to plyr.
--
Spencer Graves, PE, PhD
President and Chief Technology Officer
Structure Inspection and Monitoring, Inc.
751 Emerson Ct.
San José, CA 95126
ph: 408-655-4567
web: www.structuremonitoring.com
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