[R] basic plot() question
Peter Dalgaard BSA
p.dalgaard at biostat.ku.dk
Sun Dec 10 22:02:29 CET 2000
Tord Snall <tord.snall at ebc.uu.se> writes:
> Dear all,
> I try to plot a logstic regression model as follows:
>
> Valkror<- read.table("Valkror.txt", header=T)
> np.bark<- glm(Npinc~bark, family=binomial, data=Valkror)
> plot.formula(np.bark$fitted.values~ Valkror$bark)
>
> The above looks nice but I want to connect the points with a line so I try:
>
> plot.formula(np.bark$fitted.values~ Valkror$bark, type="b")
>
> but it gives a somewhat! unexpected figure. :(
>
> Could someone please give a clue....
Not having your data, I can't see what is wrong with your plot, but
I'd wager that it is because the x values are out of sequence. You
could try
Valkror2<-Valkror[order(Valkror$bark),]
and then
plot(predict(np.bark,Valkror2,type="response")~Valkror2$bark,type="b")
which is also safer than your strategy in case there are missing
values in your data.
--
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
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