Stat Stat - 2 months ago 26
R Question

Extract Residual Deviance from anova (glm) in R

I fitted a glm model in R and took the anova table. I need to extract the "Residual Deviance" column. But it generates an error. Here are the codes:

Creating data:

counts <- c(18,17,15,20,10,20,25,13,12)
outcome <- gl(3,1,9)
treatment <- gl(3,3)


Fitting GLM:

glm.D93 <- glm(counts ~ outcome + treatment, family = quasipoisson(link = "log"))


Anova table:

av.1=anova(glm.D93)
av.1
Analysis of Deviance Table

Model: quasipoisson, link: log

Response: counts

Terms added sequentially (first to last)


Df Deviance Resid. Df Resid. Dev
NULL 8 10.5814
outcome 2 5.4523 6 5.1291
treatment 2 0.0000 4 5.1291


Now I need to extract "Resid. Dev" column. So I tried
str


> str(av.1)
Classes ‘anova’ and 'data.frame': 3 obs. of 4 variables:
$ Df : int NA 2 2
$ Deviance : num NA 5.45 0
$ Resid. Df : int 8 6 4
$ Resid. Dev: num 10.58 5.13 5.13
- attr(*, "heading")= chr "Analysis of Deviance Table\n\nModel: quasipoisson, link: log\n\nResponse: counts\n\nTerms added sequentially (first to last)\n\"| __truncated__


Finally I extracted
Resid. Dev
but it gives me an error:

> av.1$Resid. Dev
Error: unexpected symbol in "av.1$Resid. Dev"

Answer

Use quotation marks

> av.1$"Resid. Dev"
[1] 10.581446  5.129141  5.129141

Equivalently

av.1[["Resid. Dev"]]
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