problems with abline in a time line scatterplot
On Dec 22, 2010, at 6:14 PM, tilapia wrote:
Hello R-Users
i'm stuck with the following problem:
i want to add a trend line to a scatterplot. the x axis is a time
line.
well it doesnt work, it seems that the function abline is not able
to handle the fact, that i used the column Date as a factor.
this is the script:
data<-read.table('DO_hapa_all_morning.txt',header=T,as.is=2)
So you have either character or numeric variables and very likely the column named Date is a character variable.
attach(data) names(data) plot(DO,axes=F,xlab="Date",ylab="DO [mg/l]",ylim=c(0,12),col="red") axis(1,at=1:length(DO),labels=Date) axis(2) abline(lm(DO~Date),col="red")
You will be getting a separate estimate for each separate Date other than the first.
this warning message shows up (last row translated from german): warning: 1: In model.matrix.default(mt, mf, contrasts) : variable 'Date' converted to a factor 2: In abline(lm(DO ~ Date), col = "red") : use only the first two of 54 regression coefficients is abline not the right function,
The problem lies in your lack of knowledge about how to convert a character vector into a data vector as well as you lack of understanding regarding lm(). Once you correct these deficits then abline will probably work as intended.
David > or is there a possibiliy to solve it with > the way i started it? > > > thank you for any guidance! > > Chris > > > -- > View this message in context: http://r.789695.n4.nabble.com/problems-with-abline-in-a-time-line-scatterplot-tp3161401p3161401.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help at r-project.org 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.