[R] sum elements of dataframe
Bill Simpson
wsi at gcal.ac.uk
Wed Oct 13 16:25:11 CEST 1999
I have the following problem.
Suppose I save the data from an experiment in the following way. There are
21 pairs of std and cf. Each pairing is an experimental condition, and 4
data values are saved. The conditions are run (and data saved) in random
order, though blocked such that all conditions are run once, then all in
random order a second time, and so on (let's say 3 or 4 repetitions)
What I want to do is to sum the data values of the repetitions. For
example, suppose I have
std cf hit miss fa cr
10 20 50 40 31 92
...
10 20 40 35 42 87
...
10 20 35 45 35 95
Then I want to sum the hit, miss, fa, and cr columns to get
10 20 125 120 108 274
totals for this condition.
So I will do
data<-read.table("data.dat",header=TRUE)
But then how do I sum data$hit etc across the reps?
If there is an alternative way to save the data to file(s) that makes this
task easier that is fine. E.g. I could save each condition to its own
file. But then I have to read in 21 files.
Thanks very much for any help.
Bill Simpson
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