From: Laura M Marx <marxlau1_at_msu.edu>

Date: Thu 21 Jul 2005 - 03:58:37 EST

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Jul 21 04:03:07 2005

Date: Thu 21 Jul 2005 - 03:58:37 EST

Sundar Dorai-Raj writes:

> Hi, Laura,

*>
**> Would ?predict.glm be better?
**>
**> plot(logarea, hempresence,
**> xlab = "Surface area of log (m2)",
**> ylab="Probability of hemlock seedling presence",
**> type="n", font.lab=2, cex.lab=1.5, axes=TRUE)
**> lines(logarea, predict(hemhem, logreg, "response"), lty=1, lwd=2)
**> lines(logarea, predict(hemyb, logreg, "response"), lty="dashed", lwd=2)
**> lines(logarea, predict(hemsm, logreg, "response"), lty="dotted", lwd=2)
**>
**> Without seeing more description of your data, this is still a guess.
**>
**> --sundar
**>
*

YES! Thank you. That solves all of the problems I was having. Thanks also to Tom Mulholland and Bill Venables for their replies.

Laura

The final code is now:

logreg <- read.table("C:/Documents and Settings/Laura/Desktop/logreg.txt", header=TRUE, sep=",", na.strings="NA", dec=".", strip.white=TRUE)

#This is the full dataset. A hemlock row followed by a birch row might look #like: #Hemybsm logarea hempresence #1 0.054 0 #2 1.370 1

hemhem=glm(hempresence~logarea, family=binomial(logit), subset=Hemybsm<2)
#This pulls out only the hemlocks from the full dataset and calculates the
#regression.

hemyb=glm(hempresence~logarea, family=binomial(logit), subset=Hemybsm==2)
#Same code, with only the birches from the full dataset.
hemsm=glm(hempresence~logarea, family=binomial(logit), subset=Hemybsm>2)

plot(logarea, hempresence, xlab = "Surface area of log (m2)",

ylab="Probability of hemlock seedling presence", type="n", font.lab=2, cex.lab=1.5, axes=TRUE)

lines(logarea, predict(hemhem, logreg, "response"), lty=1, lwd=2) lines(logarea, predict(hemyb, logreg, "response"), lty="dashed", lwd=2) lines(logarea, predict(hemsm, logreg, "response"), lty="dotted", lwd=2) ______________________________________________R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Jul 21 04:03:07 2005

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