Problems plotting and regression w.r.t. date data type on x axis
Hi
-----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r- project.org] On Behalf Of Kategoricus Sent: Thursday, February 14, 2013 12:25 PM To: r-help at r-project.org Subject: Re: [R] Problems plotting and regression w.r.t. date data type on x axis Hello Petr! thanks a lot for your help. The plot command plots well, but the abline returns without error and does nothing.
str(tabelle)
'data.frame': 4 obs. of 3 variables: $ date : Factor w/ 4 levels "2009-01-1","2009-12-1",..: 1 2 3 4 $ number: int 1673 2111 2487 4301 $ date2 : POSIXlt, format: "2009-01- 01" "2009-12-01" ...
As expected date is factor, number is numeric and date2 is POSIXlt format.
plot(tabelle$date2,tabelle$number, pch=19, xlab="date of retrieval", ylab="number of animals") regression.punkte<-lm(tabelle$number ~ as.Date(tabelle$date)) regression.punkte
Here you are plotting number against POSIX date2.
Call: lm(formula = tabelle$number ~ as.Date(tabelle$date))
Here you use date probably converted by as.Date. Why you do not use lm(number ~ date2, data = tabelle) which is usual form of model formula. Try also change date2 by as.POSIXct. Regards Petr
Coefficients:
(Intercept) as.Date(tabelle$date)
-24046.326 1.799
abline(regression.punkte, lwd=2)
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