I have encountered a duplicate index warning/error in zoo. I spent some time to troubleshoot, and it came down to the following data/snippet:
Lines = "Index,dbt,rh,dpt,wind.mph,gust.mph,wind.dir,voltage,klux,fc
2008-03-09 01:00:00,37.96,77.25,31.60,4.16,5.39,247,0.00,28.283,2643.28
2008-03-09 02:00:00,37.20,77.25,30.90,0.00,0.43,244,0.00,28.283,2643.28"
x <- read.table(header=T,text=Lines,sep=",")
library(zoo)
z = zoo(x[,2:10],as.POSIXct(x$Index))
If I run the above, I got the following warning:
Warning message:
In zoo(x[, 2:10], as.POSIXct(x$Index)) :
some methods for “zoo” objects do not work if the index entries in ‘order.by’ are not unique
I was wondering what is wrong with the data/index. They are in fact different.
However, the following command:
library(xts)
make.index.unique(index(z))
gave a puzzling result:
[1] "2008-03-09 01:00:00 MST" "2008-03-09 01:00:00 MST"
Did the above command just make the indeces duplicates? Can anybody enlighten me on how this works?