I have a data frame (morgan) of hourly river flow, river levels and wind
direction and speed thus:
Time hour lev.morgan lev.lock2 lev.lock1 flow direction
velocity
1 2009-07-06 15:00:00 15 3.266 3.274 3.240 1710.6 180.282
4.352
2 2009-07-06 16:00:00 16 3.268 3.272 3.240 1441.8 192.338
5.496
3 2009-07-06 17:00:00 17 3.268 3.271 3.240 1300.1 202.294
2.695
4 2009-07-06 18:00:00 18 3.267 3.274 3.241 1099.1 237.161
2.035
5 2009-07-06 19:00:00 19 3.265 3.277 3.243 986.6 237.576
0.896
6 2009-07-06 20:00:00 20 3.266 3.281 3.242 1237.6 205.686
1.257
7 2009-07-06 21:00:00 21 3.267 3.280 3.242 1513.3 26.080
0.664
8 2009-07-06 22:00:00 22 3.267 3.281 3.242 1819.5 264.280
0.646
9 2009-07-06 23:00:00 23 3.267 3.281 3.242 1954.4 337.137
0.952
10 2009-07-07 00:00:00 0 3.267 3.281 3.242 1518.9 260.006
0.562
11 2009-07-07 01:00:00 1 3.267 3.281 3.242 1082.6 252.172
0.673
12 2009-07-07 02:00:00 2 3.267 3.280 3.243 1215.9 190.007
1.286
13 2009-07-07 03:00:00 3 3.267 3.279 3.244 1093.5 260.415
1.206
: : : : : : : :
:
: : : : : : : :
:
Time is of class POSIXct
I wish to take daily means of the flow, levels, and wind parameters and put
them into a new dataframe. I envisage doing this with the following example
code:
morgan$fTime <- factor(substr(as.character(morgan$Time),1,10))
dflow <- tapply(morgan[,"flow"], morgan$fTime, mean)
day <- tapply(morgan[,"Time"], morgan$fTime, mean)
:
:
daily <- as.data.frame(cbind(day,dflow, dlev.morg,dlev.lock2, ...))
daily$day <- with(daily, as.POSIXct("1970-01-01", "%Y-%m-%d",
tz="Australia/Adelaide") + day)
rownames(daily) <- NULL
Is there a more efficient way of doing this? I am running R-2.11.0 under
Windows XP
Tschüß
Tony Meissner
Principal Scientist (Monitoring)
Resources Monitoring Group
Science, Monitoring and Information Division
Department for Water
"Imagine" ©
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