Use as.POSIXct instead of as.POSIXlt if you want to use lm() on the dates. (The data.frame() function makes this transformation for you, but you evaded data.frame() by adding the column with $<-(), which does not do the checks and transformations that data.frame() does.)
Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf > Of Marlin Keith Cox > Sent: Tuesday, December 17, 2013 12:49 PM > To: [email protected] > Subject: [R] Time series and lm > > Hello all, I have a time series defined by > > chum$Time1<-as.POSIXlt(chum$Time, format= "%m/%d/%y %H:%M") > > and a measured parameter > > pa.s > > When I create a linear model > > with(chum.skin, lm(Time1~pa.s)) > > I get the following error. > > Error in model.frame.default(formula = Time1 ~ pa.s, drop.unused.levels = > TRUE) : invalid type (list) for variable 'Time1' > I cannot figure it out. > > Keith > > > > > M. Keith Cox, Ph.D. > Principal > MKConsulting > 17105 Glacier Hwy > Juneau, AK 99801 > U.S. 907.957.4606 > > [[alternative HTML version deleted]] > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
