[R] problems with abline in a time line scatterplot
dwinsemius at comcast.net
Thu Dec 23 05:34:21 CET 2010
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
> 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:
So you have either character or numeric variables and very likely the
column named Date is a character variable.
> plot(DO,axes=F,xlab="Date",ylab="DO [mg/l]",ylim=c(0,12),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):
> 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.
> or is there a possibiliy to solve it with
> the way i started it?
> thank you for any guidance!
> 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.
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