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channelmorphology
2005 Jul 12
4
Calculation of group summaries
...nique combinations of three id variables. There
may be thousands of such combinations in the data. This is easy in SQL:
select year,
site_id,
visit_no,
mean(undercut) AS meanUndercut,
count(undercut) AS nUndercut,
std(undercut) AS stdUndercut
from channelMorphology
group by year, site_id, visit_no
;
Reading a CSV written by SAS and selecting only records expected to have
values is also straight forward in R, but getting those summary values
for each site visit is currently beyond me:
sub<-read.csv('c:/data/channelMorphology.csv'...