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The
functions tapply() and by() can be used for things like this.
E.g.,
meanBP1st3 <- tapply(dat$BP, dat$ID, function(x)
mean(x[1:3]))
HTH,
Andy
Hi,
I have a large dataset of 20000
rows that contains 180 individuals identified by a unique identification
number. There are 5 columns of data with health status data in each column,
and a different number of rows for each individual i.e. 5 rows for individual
1 and 20 rows for individual no. 2. I wish to extract the data from the first
3 rows for each individual and then perform a data function for each
individual....i.e. what is the average blood pressure for individual 1 in the
first 3 rows of their data?
I cannot seem to do this
easily...any suggestions?
Regards
Dr Bruce
Green
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