# Re: [R] lm() question

From: Christoph Scherber <Christoph.Scherber_at_agr.uni-goettingen.de>
Date: Thu, 17 Jul 2008 15:26:19 +0200

Dear Steven,

Your xlim() function is what changes the behavior of the x axis values; If you remove the xlim() statement from your function, you get a "correct" x axis:

##

YC=82:91
Age=rev(seq(2,11,1))
Num=c(2,0,8,21,49,18,79,28,273,175)
box44=data.frame(YC,Age,Num)

mod1=lm(log(Num+1)~YC, data=box44)

plot(log(Num+1)~YC, data=box44, pch=19, xlab="Year Class",

ylab="Loge Number at age", ylim=c(0,6)) abline(lm(log(Num+1)~YC), col="blue", lwd=2)

##

But what kind of graph do you want to arrive at in the end?

Best wishes
Christoph

Ranney, Steven schrieb:
> I have data that looks like
>
> YC Age Num
> 82 11 2
> 83 10 0
> 84 9 8
> 85 8 21
> 86 7 49
> 87 6 18
> 88 5 79
> 89 4 28
> 90 3 273
> 91 2 175
>
> with a program
>
> mod1=lm(log(Num+1)~YC, data=box44)
> plot(log(Num+1)~YC, data=box44, pch=19, xlab="Year Class",
> ylab="Loge Number at age", ylim=c(0,6), xlim=c(91,82))
> abline(lm(log(Num+1)~YC), col="blue", lwd=2)
> summary(mod1)
>
> I need to regress log(Num+1) against YC, but in descending (91 - 82) order so as to get a negative slope and positive intercept. I can plot the values such that the regression line appears correct (the xlim statement), but I can't figure out how to force the regression from YC 91 through 82. A call to the rev() function in front of YC does not produce the results I'm looking for.
>
> More than likely, I'm overlooking something. Thanks for any help you can provide.
>
> SR
>
> Steven H. Ranney
> USGS Montana Cooperative Fishery Research Unit
> Montana State University
> PO Box 173460
> Bozeman, MT 59717-3460
>
> phone: (406) 994-6643
> fax: (406) 994-7479
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help_at_r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> and provide commented, minimal, self-contained, reproducible code.
>
> .
>

```--
Dr. rer.nat. Christoph Scherber
University of Goettingen
DNPW, Agroecology
Waldweg 26
D-37073 Goettingen
Germany

phone +49 (0)551 39 8807
fax   +49 (0)551 39 8806

Homepage http://www.gwdg.de/~cscherb1

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