What does it mean when an anova analysis between two models doesn't produce a p-value in R?

Question

I have two small data sets:

infected.data.r.p <- structure(list(MLH = c(0.520408163265306, 0.436170212765957, 
0.344086021505376, 0.423076923076923, 0.406976744186047), ColGrowthCL_6 = c(5.923728814, 
0.283950617, 0.377358491, 1.728070175, 0.2)), .Names = c("MLH", 
"ColGrowthCL_6"), row.names = c("12", "22", "28", "30", "34"), class = "data.frame")

and

uninfected.sampling <- structure(list(MLH = c(0.524271844660194, 0.457446808510638, 
0.354838709677419, 0.398058252427184, 0.436893203883495), ColGrowthCL_6 = c(4.401639344, 
4.827586207, 6.387096774, 6.320754717, 4.225490196)), .Names = c("MLH", 
"ColGrowthCL_6"), row.names = c("218", "18", "21", "212", "99"
), class = "data.frame")

When I try to compare these two models using the anova() syntax in R (see below), it fails to produce a p-value. I'm not convinced that it is the nature of the two data sets that's causing the problem (although I'm also curious what exactly is different between the structure of the two data sets), but I suppose it very well could be the problem. Thank you!

Model comparison syntax:

infected.model<-glm(formula=as.formula(ColGrowthCL_6~MLH), family=poisson, infected.data.r.p)
uninfected.model<-glm(formula=as.formula(ColGrowthCL_6~MLH), family=poisson, uninfected.sampling)    

compare<-anova(infected.model,uninfected.model,test="Chisq")
print(compare)
summary(compare)

Answer 1

I believe you can only compare models that come from the same data set. So when comparing two (nested) models with Chi Squared, it needs to be from the same dataset - perhaps that is why your p-values aren't being calculated.