On Feb 23, 2012, at 1:41 PM, Michael Karol wrote:
R Experts
I wish to tabulate into one data frame statistics summarizing
concentration data. The summary is to include mean, standard
deviation, median, min and max. I wish to have summaries by Dose, Day
and Time. I can do this by calling aggregate once for each of the
statistics (mean, standard deviation, median, min and max) and then
execute 4 merges to merging the 5 data frames into one. (Example
aggregate code for mean only is shown below.)
Can someone show me the coding to do this as one command, rather than
5 calls to aggregate and 4 merges. In other words, in essence, I'd
like
to present to "FUN =" a list of functions, so all the summary stats
come
back in one data frame. Your assistance is appreciated. Thank you.
Perhaps something like this?
MeansByDoseDayTime <- aggregate(as.double(DF$Concentration), by =
list(DF$Dose, DF$Day, DF$Time), FUN =
function(x) c( mean(x, trim = 0, na.rm = T, weights=NULL),
sd(x, na.rm=TRUE),
median(x, na.rm=TRUE),
min(na.rm=TRUE),
max(x, na.rm=TRUE)
)
)
David Winsemius, MD
West Hartford, CT
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