Hi,
you could have a look at the doBy package which makes these operations
easier. Hadley's plyr package is also another option.
baptiste
On 20 Mar 2009, at 01:01, Altaweel, Mark R. wrote:
Hi,
I am trying to perform various functions on a list with a number of
elements. For example. I would like to take the mean of different
variable values in the entire list. As an example,
say I have a list with 1000 elements and variables called Id and
Tick. What I would like to do is take the mean of a variable called
X for each Tick in the data element. So, there can be say 1 to 600
tick values per element in a list, that would mean I would like to
find the 600 mean values for each of the ticks values in the 1000
elements.
I tried a simple attempt below, but I am sure it is way off as it
didn't produce what I expected:
//res=res[[1..1000]]
weightX<-sapply(res, function(.df) {mean(.df$X[.df$Id>0 & .df
$Tick<601])})
Basically, I was trying to get the mean for all tick values less
than 600 that have an Id variable greater than 0. So, since there
are 600 ticks I would like to return a result with 600 mean values,
for each of the 600 ticks, that factors all the 1000 occurrences of
each tick, starting from 1.
I hope this is clear. Thanks in advance.
Mark
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_____________________________
Baptiste Auguié
School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK
Phone: +44 1392 264187
http://newton.ex.ac.uk/research/emag
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