[R] merge.zoo produces non unique chron time series

[Jan Schwanbeck]

Dear all,

merge.zoo produces duplicated time indexes in the example stated below. 
Can anybody explain, what I am doing wrong?

Many thanks!

Jan

(R 2.10.0, WindowsXP)

require(chron)
require(zoo)

# create time series (zoo.ts) with no data from 31Aug2009 14:50 to 
3Sep2009 7:25
t.st <- chron("31/08/2009","09:20:00",format=c("d/m/Y","h:m:s"))
t.nd <- chron("31/08/2009","14:50:00",format=c("d/m/Y","h:m:s"))
t.indexA<-seq(t.st,t.nd,by=1/(24*12))

t.st <- chron("03/09/2009","07:25:00",format=c("d/m/Y","h:m:s"))
t.nd <- chron("03/09/2009","23:55:00",format=c("d/m/Y","h:m:s"))
t.indexB<-seq(t.st,t.nd,by=1/(24*12))

t.index<-c(t.indexA,t.indexB)

zoo.ts <- zoo(0,t.index)

# create reference time series (zoo.ts.pot) without missing time steps
t.st <- head(time(zoo.ts),1)
t.nd <- tail(time(zoo.ts),1)
t.index<-seq(t.st,t.nd,by=1/(24*12))
zoo.ts.pot <- zoo(NA,t.index)

# merge erroneous time series with reference time series
zoo.ts.cor <- merge.zoo(zoo.ts.pot,zoo.ts)

####################################
#################### Do not run: Results:
                               zoo.ts.pot zoo.ts
(31/08/09 09:20:00)         NA      0
(31/08/09 09:25:00)         NA      0
(31/08/09 09:30:00)         NA      0
...
(31/08/09 14:50:00)         NA      0
(31/08/09 14:55:00)         NA     NA
(31/08/09 15:00:00)         NA     NA
(31/08/09 15:05:00)         NA     NA
...
(03/09/09 07:15:00)         NA     NA
(03/09/09 07:20:00)         NA     NA
(03/09/09 07:25:00)         NA      0
(03/09/09 07:30:00)         NA      0
(03/09/09 07:35:00)         NA      0
(03/09/09 07:40:00)         NA      0
(03/09/09 07:45:00)         NA      0
(03/09/09 07:50:00)         NA      0
(03/09/09 07:55:00)         NA      0
(03/09/09 08:00:00)         NA      0
# everything o.k. up to here
(03/09/09 08:00:00)         NA     NA
# from here: every tenth time stamp is duplicated. Why?
...
(03/09/09 08:45:00)         NA      0
(03/09/09 08:45:00)         NA     NA
..
(03/09/09 09:30:00)         NA      0
(03/09/09 09:30:00)         NA     NA
...