Adding a subset to a glm messes up factors?
First, 'subset' is an argument to glm(), but for some reason you did not use it. Your subject line is quite misleading, and had it been the more accurate Adding a 'data' argument to glm messes up factors? you might have realised the problem. Second, your models are fitted to different datasets: the first to objects in your workspace, and the second to columns of data.all. Since you have not (as we asked) given a reproducible example we cannot know what those differences are, but differences in the datasets will be the key. Third, the best way to fit linear models is lm(), not glm(family=gaussian).
On Fri, 7 Dec 2007, Muri Soares wrote:
I have a problem with running a glm using a subset of my data. Whenever I choose a subset, in the summary the factors arent shown (as if the variable was a continuous variable). If I dont use subsets then all the factors are shown. I have copied the output from summary for both cases. Thanks for the help, Muri
model<-glm(log(cpue)~year,family=gaussian)
Call:
glm(formula = log(cpue) ~ year, family = gaussian)
Deviance Residuals:
Min 1Q Median 3Q Max
-2.0962 -0.5851 -0.1241 0.4805 3.9236
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 0.8899 0.1844 4.825 1.42e-06 ***
year1990 -0.6107 0.1925 -3.173 0.00152 **
year1991 -1.7466 0.1902 -9.184 < 2e-16 ***
year1992 -1.4061 0.1864 -7.544 5.07e-14 ***
year1993 -1.4069 0.1860 -7.565 4.31e-14 ***
...
model<-glm(log(cpue)~year,family=gaussian,subset(data.all,species=="n")
Call:
glm(formula = log(cpue) ~ year, family = gaussian, data = subset(data.all,
species == "n"))
Deviance Residuals:
Min 1Q Median 3Q Max
-1.64577 -0.61671 -0.08972 0.55792 2.73737
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 32.446570 10.076895 3.220 0.00135 **
year -0.016345 0.005037 -3.245 0.00123 **
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