Hi most probably your dates are not what you expect. Eg. they look like a date but they are not treated as date. You can check yourself by
str(tabelle) which will result probably in factor, numeric, factor. You need to change variables date and date2 into Date class. ?strptime or ?as.Date date and date2 seems to be same but usually you shall use the same variables for plotting and for model to get correct regression line. Regards Petr > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Kategoricus > Sent: Thursday, February 14, 2013 10:10 AM > To: r-help@r-project.org > Subject: [R] Problems plotting and regression w.r.t. date data type on > x axis > > Hello, > > probably a newbie question, but i didnt find any information on > plotting/regressing w.r.t. a date data type. My trials were unfruitful. > Can anyone help ? Thanks in advance! > > Here is my interaction with R: > > > > tabelle > date number date2 > 1 2009-01-1 1673 2009-01-01 > 2 2009-12-1 2111 2009-12-01 > 3 2010-7-1 2487 2010-07-01 > 4 2013-2-1 4301 2013-02-01 > > regression.punkte<-lm(tabelle$number ~ tabelle$date2) > Fehler in model.frame.default(formula = tabelle$number ~ tabelle$date2, > : > ungültiger Typ (list) für die Variable 'tabelle$date2' > > regression.punkte<-lm(tabelle$number ~ tabelle$date) > > plot(tabelle$date2,tabelle$number, pch=19, xlab="date of retrieval", > > ylab="number of animals") ***R DRAWS THIS*** regression.punkte > > Call: > lm(formula = tabelle$number ~ tabelle$date) > > Coefficients: > (Intercept) tabelle$date2009-12-1 tabelle$date2010-7-1 > 1673 438 814 > tabelle$date2013-2-1 > 2628 > > > abline(regression.punkte, lwd=2) ***R DOES NOT DRAW LINE*** > Warnmeldung: > In abline(regression.punkte, lwd = 2) : > nutze nur die ersten beiden von 4 Regressionskoeffizienten > > summary(regression.punkte) > > Call: > lm(formula = tabelle$number ~ tabelle$date) > > Residuals: > ALL 4 residuals are 0: no residual degrees of freedom! > > Coefficients: > Estimate Std. Error t value Pr(>|t|) > (Intercept) 1673 NA NA NA > tabelle$date2009-12-1 438 NA NA NA > tabelle$date2010-7-1 814 NA NA NA > tabelle$date2013-2-1 2628 NA NA NA > > Residual standard error: NaN on 0 degrees of freedom Multiple R- > squared: 1, Adjusted R-squared: NaN > F-statistic: NaN on 3 and 0 DF, p-value: NA > > > > -- > View this message in context: http://r.789695.n4.nabble.com/Problems- > plotting-and-regression-w-r-t-date-data-type-on-x-axis-tp4658518.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@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. ______________________________________________ R-help@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.
