I'm very new to R and get some trouble to interpret. Here is the code
Crabs <- read.table("http://www.stat.ufl.edu/~aa/cat/data/Crabs.dat",
header = TRUE)
fit <- glm(y ~ width + factor(color), family = binomial, data = Crabs)
summary(fit)
And the output is
Call:
glm(formula = y ~ width + factor(color), family = binomial, data = Crabs)
Deviance Residuals:
Min 1Q Median 3Q Max
-2.1124 -0.9848 0.5243 0.8513 2.1413
Coefficients:
Estimate Std. Error z value Pr(>|z|)
(Intercept) -11.38519 2.87346 -3.962 7.43e-05 ***
width 0.46796 0.10554 4.434 9.26e-06 ***
factor(color)2 0.07242 0.73989 0.098 0.922
factor(color)3 -0.22380 0.77708 -0.288 0.773
factor(color)4 -1.32992 0.85252 -1.560 0.119
---
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
(Dispersion parameter for binomial family taken to be 1)
Null deviance: 225.76 on 172 degrees of freedom
Residual deviance: 187.46 on 168 degrees of freedom
AIC: 197.46
Number of Fisher Scoring iterations: 4
Q1: In sector 'Coefficients:' there is no 'factor(color)1' but others. Why?
Q2: What's the difference between 'Null deviance' and 'Residual deviance'
Q3: What does 'AIC' mean?
Could I please have some help? Short answer is fine