Revisions to Interpreting plot of residuals vs. fitted values from Poisson regression

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edited Aug 23 at 14:52

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I am trying to fit data with a GLM (poisson regression) in R. When I plotted the residuals vs the fitted values, the plot created multiple (almost linear with a slight concave curve) "lines". What does this mean?

library(faraway)
modl <- glm(doctorco ~ sex + age + agesq + income + levyplus + freepoor + 
            freerepa + illness + actdays + hscore + chcond1 + chcond2,
            family=poisson, data=dvisits)
plot(modl)

library(faraway)
modl <- glm(doctorco ~ sex + age + agesq + income + levyplus + freepoor + 
                freerepa + illness + actdays + hscore + chcond1 + chcond2,
                family=poisson, data=dvisits)
plot(modl)

enter image description here

I am trying to fit data with a GLM (poisson regression) in R. When I plotted the residuals vs the fitted values, the plot created multiple (almost linear with a slight concave curve) "lines". What does this mean?

library(faraway)
modl <- glm(doctorco ~ sex + age + agesq + income + levyplus + freepoor + 
            freerepa + illness + actdays + hscore + chcond1 + chcond2,
            family=poisson, data=dvisits)
plot(modl)

enter image description here

I am trying to fit data with a GLM (poisson regression) in R. When I plotted the residuals vs the fitted values, the plot created multiple (almost linear with a slight concave curve) "lines". What does this mean?

library(faraway)
modl <- glm(doctorco ~ sex + age + agesq + income + levyplus + freepoor + 
                freerepa + illness + actdays + hscore + chcond1 + chcond2,
                family=poisson, data=dvisits)
plot(modl)

enter image description here