Hi,
Try:
set.seed(45)
df1<-
data.frame(datetime=as.POSIXct("2011-05-25",tz="GMT")+1:200,value=sample(1:40,200,replace=TRUE),value2=
sample(45:90,200,replace=TRUE))
res<-
with(df1,aggregate(cbind(value,value2),list(as.POSIXct(cut(datetime,breaks="5
sec"))+4),mean))
colnames(res)[1]<- colnames(df1)[1]
head(res)
# datetime value value2
#1 2011-05-25 00:00:05 16.0 67.4
#2 2011-05-25 00:00:10 10.8 60.0
#3 2011-05-25 00:00:15 20.2 65.2
#4 2011-05-25 00:00:20 17.8 65.2
#5 2011-05-25 00:00:25 21.2 81.6
#6 2011-05-25 00:00:30 21.4 56.2
#or
library(plyr)
res2<- ddply(df1,.(datetime=as.POSIXct(cut(df1$datetime,breaks="5 sec"))+4
),numcolwise(mean))
head(res2)
# datetime value value2
#1 2011-05-25 00:00:05 16.0 67.4
#2 2011-05-25 00:00:10 10.8 60.0
#3 2011-05-25 00:00:15 20.2 65.2
#4 2011-05-25 00:00:20 17.8 65.2
#5 2011-05-25 00:00:25 21.2 81.6
#6 2011-05-25 00:00:30 21.4 56.2
#or
library(xts)
originalTZ <- Sys.getenv("TZ")
Sys.setenv(TZ = "GMT")
xt1<- xts(df1[,2:3],order.by=df1[,1])
indx<-endpoints(xt1,'secs',5)
res3<-period.apply(xt1,c(0,indx[-c(1,length(indx))]+1),FUN=mean)
head(res3)
# value value2
#2011-05-25 00:00:05 16.0 67.4
#2011-05-25 00:00:10 10.8 60.0
#2011-05-25 00:00:15 20.2 65.2
#2011-05-25 00:00:20 17.8 65.2
#2011-05-25 00:00:25 21.2 81.6
#2011-05-25 00:00:30 21.4 56.2
Sys.setenv(TZ = originalTZ)
A.K.
Hi, I am new to R and to this forum.
I have to do a project for school and I have to calculate the mean
of a set of values corresponding to certain times (in two columns).
I will need to calculate the mean of the values every K seconds and I
dont know how to divide my Time column or to link the values to their
corresponding period.
Could you give me a hand on this?
Cheers!
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