Almost except
tapply(x[4:8], x$interval, colMeans)
works but with a larger data frame I have problems, even
tapply(x[4:7], x$interval, colMeans)
gets the "arguments must have the same length" error. But they do! Any
ideas?
Thanks for your help Jim
On 12/19/2011 2:00 PM, jim holtman wrote:
Does this work for you:
x<- read.table(text = " date time Voltage LwTempDownelling LwDownwelling
LwDownwelling_min LwDownwelling_max LwTempUpwelling
+ 1 2011-11-01 00:00:00 2.732447 17.30 30.0
14.0 39.5 17.83
+ 2 2011-11-01 00:10:00 2.731534 17.46 15.3
11.1 24.6 17.95
+ 3 2011-11-01 00:20:00 2.731368 17.43 28.7
24.6 30.7 17.93
+ 4 2011-11-01 00:30:00 2.730703 17.36 40.4
29.8 43.5 17.86
+ 5 2011-11-01 00:40:00 2.729567 17.26 41.6
40.5 42.6 17.76"
+ , header = TRUE
+ )
# convert the time
x$timestamp<- as.POSIXct(paste(x$date, x$time))
# calculate the start of time ranges
start<- trunc(min(x$timestamp), units = 'hour')
# create breakpoints at 30 minutes
breaks<- seq(from = start
+ , to = max(x$timestamp) + 3600 # make sure you have the
last range
+ , by = '30 min'
+ )
# slice up the data by adding index
x$interval<- findInterval(x$timestamp, breaks)
# determine colMeans
newData<- do.call(rbind, tapply(x[4:8], x$interval, colMeans))
newData<- as.data.frame(newData)
# add the time back
newData$timestamp<- breaks[as.integer(rownames(newData))]
newData
LwTempDownelling LwDownwelling LwDownwelling_min LwDownwelling_max
LwTempUpwelling
1 17.39667 24.66667 16.56667 31.60
17.90333
2 17.31000 41.00000 35.15000 43.05
17.81000
timestamp
1 2011-11-01 00:00:00
2 2011-11-01 00:30:00
On Mon, Dec 19, 2011 at 4:28 AM, Mathew Brown
<mathew.br...@forst.uni-goettingen.de> wrote:
Hi there,
This seems like it should be simple. I have a data frame of climate data
sampled every 10 min. I want to average the entire data frame into 30
min values (i.e., one value for each half hour). Functions like
running.mean give me a moving average but I want to reduce the size of
the entire frame.. Any ideas how? Cheers!
Example of my data
timestamp Voltage LwTempDownelling LwDownwelling LwDownwelling_min
LwDownwelling_max LwTempUpwelling
1 2011-11-01 00:00:00 2.732447 17.30 30.0 14.0
39.5 17.83
2 2011-11-01 00:10:00 2.731534 17.46 15.3 11.1
24.6 17.95
3 2011-11-01 00:20:00 2.731368 17.43 28.7 24.6
30.7 17.93
4 2011-11-01 00:30:00 2.730703 17.36 40.4 29.8
43.5 17.86
5 2011-11-01 00:40:00 2.729567 17.26 41.6 40.5
42.6 17.76
6 2011-11-01 00:50:00 2.728976 17.16 39.7
-M.B
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