Warning message when using read.zoo function - r

Question

I have data frame(df) that contains daily stock index prices covering over 4000 days. It looks like:
Date Prices
1986-1-1 20
. .
. .
. .
. .
2001-08-31 40
I am trying to convert the data frame into zoo object using read.zoo(df) (read.zoo is a function in zoo package). However it gives me the following error:
Warning message:
In zoo(rval3, ix) :
some methods for “zoo” objects do not work if the index entries in ‘order.by’ are not unique
that affects the subsequent codes I apply to the object.
For a reproducibility purpose, the original data (FTSE100jensen.csv) and code (JensenPaper.R) is available on https://github.com/ahmedfsalhin/1stpaper

Answer 1

The problem is that you called read.zoo() without providing a value for format=, but your dates are formated like "%d/%m/%Y", not "%Y-%m-%d"

Answer 2

I'm not quite sure why this error was occurring, but I first converted Date to the Date class and was able to call read.zoo without error using this:
options(stringsAsFactors=FALSE)
library(zoo)
##
Data <- read.csv(
"F:/gitData.csv",
header=TRUE)
#
Data$Date <- as.Date(
Data$Date,
"%d/%m/%Y")
##
zData <- read.zoo(Data)
##
> head(zData)
Open High Low Close Volume Adj.Close
1986-01-01 1412.6 1412.6 1412.6 1412.6 0 1412.6
1986-01-02 1412.6 1420.8 1412.0 1420.5 0 1420.5
1986-01-03 1420.5 1430.0 1419.6 1429.8 0 1429.8
1986-01-06 1429.8 1436.3 1424.1 1424.1 0 1424.1
1986-01-07 1419.8 1419.8 1411.6 1415.2 0 1415.2
1986-01-08 1415.2 1419.3 1400.3 1404.2 0 1404.2
and everything seems to be in order, e.g. I can call .zoo methods properly, etc...
> plot(zData)
To address the comments above, the error message does seem to indicate that there are duplicated dates, but this is not the case:
> dim(Data)
[1] 4088 7
> length(unique(Data$Date))
[1] 4088