When transforming the below data (class "zoo") into xts, I use returns.xts<-as.xts(returns). The effect is to add quotation marks around the new Data. And then becomes unusable in functions.
Why is this?
class("zoo")
UK.EQUITY EUR.EQUITY NA.EQUITY ASIA.EQUITY JPN.EQUITY EM.EQUITY WORLD.EQUITY.EX.UK
2006-04-30 0.010552982 -0.003337229 -0.033739353 0.025092643 -0.020920633 0.020016007 -0.021165353
2006-05-31 -0.048962517 -0.071924029 -0.059684763 -0.102475485 -0.098121902 -0.141877111 -0.067793295
class ("zoo" "xts")
UK.EQUITY EUR.EQUITY NA.EQUITY ASIA.EQUITY JPN.EQUITY EM.EQUITY
2006-04-30 "0.010552982" "-0.003337229" "-0.033739353" "0.025092643" "-0.020920633" "0.020016007"
2006-05-31 "-0.048962517" "-0.071924029" "-0.059684763" "-0.102475485" "-0.098121902" "-0.141877111"
xts is not "adding quotation marks". xts prints character data with quotation marks, but zoo does not. str(returns) and str(as.xts(returns)) should both show that the coredata of the objects is character. This is because "#N/A" cannot be converted to a number.
You don't say how you're reading from Excel (though the tags you added suggest you are), but there are usually ways to specify how NA values are represented. For example, read.csv has a na.strings argument you can set to "#N/A".