Hi
r-help-boun...@r-project.org napsal dne 11.02.2010 20:36:31:
>
> Hello,
>
> With a dataset that is about 1.4e6 rows long
> my.dat[seq(1:20),]
> date Cell_ID Classification WT_Depth Frac_ET_Satsfd
> 1999-04-08 974 3 3.585083 0.244561400
> 1999-04-08 1188 3 3.526001 0.123484700
> 1999-04-08 1189 3 3.187012 0.215916700
> 1999-04-08 1403 3 3.395020 0.163972900
> 1999-04-08 1409 3 2.368042 0.415165500
> 1999-04-08 1617 3 4.039917 0.003224544
> 1999-04-08 1618 3 3.457886 0.148585900
> 1999-04-08 1619 3 2.148926 0.475924300
> 1999-04-08 1620 2 1.523926 0.633190900
> 1999-04-08 1621 3 2.197998 0.469294300
> 1999-04-15 1622 7 2.759033 0.325698400
> 1999-04-15 1623 3 2.802002 0.313719600
> 1999-04-15 1624 3 3.062988 0.243275900
> 1999-04-15 1833 2 3.483032 0.141840700
> 1999-04-15 1834 2 3.128052 0.232235400
> 1999-04-15 1835 7 3.354004 0.176209000
> 1999-04-15 1836 3 2.691040 0.341234700
> 1999-04-15 1837 3 3.140991 0.228083800
> 1999-04-15 1838 3 2.392944 0.413379300
> 1999-04-15 2048 2 3.712036 0.084534560
> .
> .
> .
> I use
> edm.func<-function(x){c(mu=mean(x),var=var(x))}
>
output<-do.call("rbind",tapply(my.dat$Frac_ET_Satsfd,list(my.dat$date,my.dat
> $Classification),edm.func))
> data.frame(output)
> mu var
> 1 0.7980007 0.03446669
> 2 0.7947966 0.03429280
> 3 0.8240736 0.02482441
> .
> .
> 3573 0.4509044 0.03821251
> 3574 0.4484108 0.03856110
> 3575 0.4519150 0.03889944
>
> There are 447 dates and 8 classifications (1-8). What is the best way
to
> include the corresponding date and classification that goes with each
row?
I would use different approach to get summary values. One option is
cbinding aggregate results
aggregate(my.dat$Frac_ET_Satsfd,list(my.dat$date,my.dat$Classification),
mean)
aggregate(my.dat$Frac_ET_Satsfd,list(my.dat$date,my.dat$Classification),
sd)
The other is to use by which accepts function returning several values.
Other possibility is sapply/split approach, which I believe is used in
plyr library
output<-
t(sapply(split(my.dat$Frac_ET_Satsfd,interaction(my.dat$date,my.dat$Classification),edm.func)))
Untested, not sure about parentheses.
Regards
Petr
>
> Thanks Eric
> --
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> tp1477702p1477702.html
> Sent from the R help mailing list archive at Nabble.com.
>
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