Please help to solve that problem:
filter and merge 2 big Df's by=t_chr in sec.
require(zoo)
t1="2012-03-25 17:00:00.0"
t2="2012-03-25 17:00:05.0"
t1_POSIXlt<-strptime(t1, "%Y-%m-%d %H:%M:%OS")#
t2_POSIXlt<-strptime(t2, "%Y-%m-%d %H:%M:%OS")#
# ts_t1t2_POSIXlt<-seq(t1_POSIXlt,t2_POSIXlt,length.out
=-1+2*length(seq(t1_POSIXlt,t2_POSIXlt, "sec") ) )
ts_t1t2_POSIXlt<-seq(t1_POSIXlt,t2_POSIXlt,length.out
=length(seq(t1_POSIXlt,t2_POSIXlt, "sec") ) )
t_ts_t1t2_chr<-as.character(format(ts_t1t2_POSIXlt,"%Y-%m-%d %H:%M:%OS"))
tail(t_ts_t1t2_chr)
t_chr<-rep(t_ts_t1t2_chr,c((1:(-1+length(t_ts_t1t2_chr))),1))
str(t_chr)
# system.time()
Df.a<-as.data.frame(cbind(t_chr,a=c(1:length(t_chr)),b=2*c(1:length(t_chr)),c=0.1*c(length(t_chr):1)));
Df.a
#----------------------------------------
#We wants to obtain" for each single second (time as a key) a) mean filtered
t_chr a b c
2012-03-25 17:00:00 1 2 1.6
2012-03-25 17:00:01 2.5 5 1.45
2012-03-25 17:00:02 5 10 1.2
2012-03-25 17:00:03 8.5 17 0.85
2012-03-25 17:00:04 13 26 0 0.4
2012-03-25 17:00:05 16 32 0.1
Df.a.filtered.mean=???
#------------------------------------------
#We wants to obtain" for each single second (time as a key)
b) max filtered
#key = time, each second: 1 max from these same seconds
t_chr a b c
1 2012-03-25 17:00:00 1 2 1.6
3 2012-03-25 17:00:01 3 6 1.5
6 2012-03-25 17:00:02 6 12 1.3
10 2012-03-25 17:00:03 10 20 1.0
10 2012-03-25 17:00:04 15 30 1.0
16 2012-03-25 17:00:05 16 32 0.1
Df.a.filtered.max =???
#------------------------------------------
the problem is, taht we have huge matrix. The solution should be fast.
next we want to merge it with another Data frame
#------------------------------------------
t1="2012-03-25 17:00:00.0"
t2="2012-03-25 17:00:05.0"
t1_POSIXlt<-strptime(t1, "%Y-%m-%d %H:%M:%OS")#
t2_POSIXlt<-strptime(t2, "%Y-%m-%d %H:%M:%OS")#
ts_t1t2_POSIXlt<-seq(t1_POSIXlt,t2_POSIXlt,length.out
=-1+2*length(seq(t1_POSIXlt,t2_POSIXlt, "sec") ) )
# ts_t1t2_POSIXlt<-seq(t1_POSIXlt,t2_POSIXlt,length.out
=length(seq(t1_POSIXlt,t2_POSIXlt, "sec") ) )
t_chr2<-t_ts_t1t2_chr<-as.character(format(ts_t1t2_POSIXlt,"%Y-%m-%d
%H:%M:%OS"))
tail(t_ts_t1t2_chr)
Df.b<-as.data.frame(cbind(t_chr2,dfb.b1=c(1:length(t_chr2)),dfb.b=2*c(1:length(t_chr2)),dfb.c=0.1*c(length(t_chr2):1)));
Df.b
#------------------------------------------
merge(Df.a,Df.b, by.x=t_chr,by.y=t_chr2,all.x=TRUE,all.y=TRUE)
And if in Df.a there is no all seconds measurements?
And if in Df.a. there are many NA?
How we can handle it in R?
Thanks
KaluzaEA.
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